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Borates have low toxicity in mammals (similar to table salt) but are more toxic to arthropods and are occasionally used as insecticides. Boron-containing organic antibiotics are known. Although only traces are required, it is an essential plant nutrient.
History
The word boron was coined from borax, the mineral from which it was isolated, by analogy with carbon, which boron resembles chemically.
Borax in its mineral form (then known as tincal) first saw use as a glaze, beginning in China circa 300 AD. Some crude borax traveled westward, and was apparently mentioned by the alchemist Jabir ibn Hayyan around 700 AD. Marco Polo brought some glazes back to Italy in the 13th century. Georgius Agricola, in around 1600, reported the use of borax as a flux in metallurgy. In 1777, boric acid was recognized in the hot springs (soffioni) near Florence, Italy, at which point it became known as sal sedativum, with ostensible medical benefits. The mineral was named sassolite, after Sasso Pisano in Italy. Sasso was the main source of European borax from 1827 to 1872, when American sources replaced it. Boron compounds were rarely used until the late 1800s when Francis Marion Smith's Pacific Coast Borax Company first popularized and produced them in volume at low cost.
Boron was not recognized as an element until it was isolated by Sir Humphry Davy and by Joseph Louis Gay-Lussac and Louis Jacques Thénard. In 1808 Davy observed that electric current sent through a solution of borates produced a brown precipitate on one of the electrodes. In his subsequent experiments, he used potassium to reduce boric acid instead of electrolysis. He produced enough boron to confirm a new element and named it boracium. Gay-Lussac and Thénard used iron to reduce boric acid at high temperatures. By oxidizing boron with air, they showed that boric acid is its oxidation product. Jöns Jacob Berzelius identified it as an element in 1824. Pure boron was arguably first produced by the American chemist Ezekiel Weintraub in 1909.
Characteristics of the element
Isotopes | Boron | Wikipedia | 466 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Boron has two naturally occurring and stable isotopes, 11B (80.1%) and 10B (19.9%). The mass difference results in a wide range of δ11B values, which are defined as a fractional difference between the 11B and 10B and traditionally expressed in parts per thousand, in natural waters ranging from −16 to +59. There are 13 known isotopes of boron; the shortest-lived isotope is 7B which decays through proton emission and alpha decay with a half-life of 3.5×10−22 s. Isotopic fractionation of boron is controlled by the exchange reactions of the boron species B(OH)3 and [B(OH)4]−. Boron isotopes are also fractionated during mineral crystallization, during H2O phase changes in hydrothermal systems, and during hydrothermal alteration of rock. The latter effect results in preferential removal of the [10B(OH)4]− ion onto clays. It results in solutions enriched in 11B(OH)3 and therefore may be responsible for the large 11B enrichment in seawater relative to both oceanic crust and continental crust; this difference may act as an isotopic signature.
The exotic 17B exhibits a nuclear halo, i.e. its radius is appreciably larger than that predicted by the liquid drop model.
NMR spectroscopy
Both 10B and 11B possess nuclear spin. The nuclear spin of 10B is 3 and that of 11B is . These isotopes are, therefore, of use in nuclear magnetic resonance spectroscopy; and spectrometers specially adapted to detecting the boron-11 nuclei are available commercially. The 10B and 11B nuclei also cause splitting in the resonances of attached nuclei.
Allotropes | Boron | Wikipedia | 369 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Boron forms four major allotropes: α-rhombohedral and β-rhombohedral (α-R and β-R), γ-orthorhombic (γ) and β-tetragonal (β-T). All four phases are stable at ambient conditions, and β-rhombohedral is the most common and stable. An α-tetragonal phase also exists (α-T), but is very difficult to produce without significant contamination. Most of the phases are based on B12 icosahedra, but the γ phase can be described as a rocksalt-type arrangement of the icosahedra and B2 atomic pairs. It can be produced by compressing other boron phases to 12–20 GPa and heating to 1500–1800 °C; it remains stable after releasing the temperature and pressure. The β-T phase is produced at similar pressures, but higher temperatures of 1800–2200 °C. The α-T and β-T phases might coexist at ambient conditions, with the β-T phase being the more stable. Compressing boron above 160 GPa produces a boron phase with an as yet unknown structure, and this phase is a superconductor at temperatures below 6–12 K.
Atomic structure
Atomic boron is the lightest element having an electron in a p-orbital in its ground state. Its first three ionization energies are higher than those for heavier group III elements, reflecting its electropositive character.
Chemistry of the element
Preparation
Elemental boron is rare and poorly studied because the pure material is extremely difficult to prepare. Most studies of "boron" involve samples that contain small amounts of carbon. Very pure boron is produced with difficulty because of contamination by carbon or other elements that resist removal.
Some early routes to elemental boron involved the reduction of boric oxide with metals such as magnesium or aluminium. However, the product was often contaminated with borides of those metals. Pure boron can be prepared by reducing volatile boron halides with hydrogen at high temperatures. Ultrapure boron for use in the semiconductor industry is produced by the decomposition of diborane at high temperatures and then further purified by the zone melting or Czochralski processes. | Boron | Wikipedia | 466 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Reactions of the element
Crystalline boron is a hard, black material with a melting point of above 2000 °C. Crystalline boron is chemically inert and resistant to attack by boiling hydrofluoric or hydrochloric acid. When finely divided, it is attacked slowly by hot concentrated hydrogen peroxide, hot concentrated nitric acid, hot sulfuric acid or hot mixture of sulfuric and chromic acids.
Since elemental boron is very rare, its chemical reactions are of little significance practically speaking. The elemental form is not typically used as a precursor to compounds. Instead, the extensive inventory of boron compounds are produced from borates.
When exposed to air, under normal conditions, a protective oxide or hydroxide layer forms on the surface of boron, which prevents further corrosion. The rate of oxidation of boron depends on the crystallinity, particle size, purity and temperature. At higher temperatures boron burns to form boron trioxide:
4 B + 3 O2 → 2 B2O3
Chemical compounds
General trends
In some ways, boron is comparable to carbon in its capability to form stable covalently bonded molecular networks (even nominally disordered (amorphous) boron contains boron icosahedra, which are bonded randomly to each other without long-range order.). In terms of chemical behavior, boron compounds resembles silicon. Aluminium, the heavier congener of boron, does not behave analogously to boron: it is far more electropositive, it is larger, and it tends not to form homoatomic Al-Al bonds. In the most familiar compounds, boron has the formal oxidation state III. These include the common oxides, sulfides, nitrides, and halides, as well as organic derivatives
Boron compounds often violate the octet rule.
Halides
Boron forms the complete series of trihalides, i.e. BX3 (X = F, Cl, Br, I). The trifluoride is produced by treating borate salts with hydrogen fluoride, while the trichloride is produced by carbothermic reduction of boron oxides in the presence of chlorine gas: | Boron | Wikipedia | 451 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
The trihalides adopt a planar trigonal structures, in contrast to the behavior of aluminium trihalides. All charge-neutral boron halides violate the octet rule, hence they typically are Lewis acidic. For example, boron trifluoride (BF3) combines eagerly with fluoride sources to give the tetrafluoroborate anion, BF4−. Boron trifluoride is used in the petrochemical industry as a catalyst. The halides react with water to form boric acid. Other boron halides include those with B-B bonding, such as B2F4 and B4Cl4.
Oxide derivatives
Boron-containing minerals exclusively exist as oxides of B(III), often associated with other elements. More than one hundred borate minerals are known. These minerals resemble silicates in some respect, although it is often found not only in a tetrahedral coordination with oxygen, but also in a trigonal planar configuration. The borates can be subdivided into two classes, anhydrous and the far more common hydrates. The hydrates contain B-OH groups and sometimes water of crystallization. A typical motif is exemplified by the tetraborate anions of the common mineral borax. The formal negative charge of the tetrahedral borate center is balanced by sodium (Na+). Some idea of the complexity of these materials is provided by the inventory of zinc borates, which are common wood preservatives and fire retardants: 4ZnO·B2O3·H2O, ZnO·B2O3·1.12H2O, ZnO·B2O3·2H2O, 6ZnO·5B2O3·3H2O, 2ZnO·3B2O3·7H2O, 2ZnO·3B2O3·3H2O, 3ZnO·5B2O3·14H2O, and ZnO·5B2O3·4.5H2O.
As illustrated by the preceding examples, borate anions tend to condense by formation of B-O-B bonds. Borosilicates, with B-O-Si, and borophosphates, with B-O-P linkages, are also well represented in both minerals and synthetic compounds. | Boron | Wikipedia | 501 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Related to the oxides are the alkoxides and boronic acids with the formula B(OR)3 and R2BOH, respectively. Boron forms a wide variety of such metal-organic compounds, some of which are used in the synthesis of pharmaceuticals. These developments, especially the Suzuki reaction, was recognized with the 2010 Nobel Prize in Chemistry to Akira Suzuki.
Hydrides
Boranes and borohydrides are neutral and anionic compounds of boron and hydrogen, respectively. Sodium borohydride is the progenitor of the boranes. Sodium borohydride is obtained by hydrogenation of trimethylborate:
Sodium borohydride is a white, fairly air-stable salt.
Sodium borohydride converts to diborane by treatment with boron trifluoride:
Diborane is the dimer of the elusive parent called borane, BH3. Having a formula akin to ethane's (C2H6), diborane adopts a very different structure, featuring a pair of bridging H atoms. This unusual structure, which was deduced only in the 1940's, was an early indication of the many surprises provided by boron chemistry.
Pyrolysis of diborane gives boron hydride clusters, such as pentaborane(9) and decaborane . A large number of anionic boron hydrides are also known, e.g. [B12H12]2−. In these cluster compounds, boron has a coordination number greater than four. The analysis of the bonding in these polyhedra clusters earned William N. Lipscomb the 1976 Nobel Prize in Chemistry for "studies on the structure of boranes illuminating problems of chemical bonding". Not only are their structures unusual, many of the boranes are extremely reactive. For example, a widely used procedure for pentaborane states that it will "spontaneously inflame or explode in air".
Organoboron compounds
A large number of organoboron compounds, species with B-C bonds, are known. Many organoboron compounds are produced from hydroboration, the addition of B-H bonds to bonds. Diborane is traditionally used for such reactions, as illustrated by the preparation of trioctylborane: | Boron | Wikipedia | 490 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
This regiochemistry, i.e. the tendency of B to attach to the terminal carbon - is explained by the polarization of the bonds in boranes, which is indicated as Bδ+-Hδ-.
Hydroboration opened the doors for many subsequent reactions, several of which are useful in the synthesis of complex organic compounds. The significance of these methods was recognized by the award of Nobel Prize in Chemistry to H. C. Brown in 1979. Even complicated boron hydrides, such as decaborane undergo hydroboration. Like the volatile boranes, the alkyl boranes ignite spontaneously in air.
In the 1950s, several studies examined the use of boranes as energy-increasing "Zip fuel" additives for jet fuel.
Triorganoboron(III) compounds are trigonal planar and exhibit weak Lewis acidity. The resulting adducts are tetrahedral. This behavior contrasts with that of triorganoaluminium compounds (see trimethylaluminium), which are tetrahedral with bridging alkyl groups.
Nitrides
The boron-nitrides follow the pattern of avoiding B-B and N-N bonds: only B-N bonding is observed generally. The boron nitrides exhibit structures analogous to various allotropes of carbon, including graphite, diamond, and nanotubes. This similarity reflects the fact that B and N have eight valence electrons as does a pair of carbon atoms. In cubic boron nitride (tradename Borazon), boron and nitrogen atoms are tetrahedral, just like carbon in diamond. Cubic boron nitride, among other applications, is used as an abrasive, as its hardness is comparable with that of diamond. Hexagonal boron nitride (h-BN) is the BN analogue of graphite, consisting of sheets of alternating B and N atoms. These sheets stack with boron and nitrogen in registry between the sheets. Graphite and h-BN have very different properties, although both are lubricants, as these planes slip past each other easily. However, h-BN is a relatively poor electrical and thermal conductor in the planar directions. Molecular analogues of boron nitrides are represented by borazine, (BH)3(NH)3.
Carbides | Boron | Wikipedia | 493 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Boron carbide is a ceramic material. It is obtained by carbothermal reduction of B2O3in an electric furnace:
2 B2O3 + 7 C → B4C + 6 CO
Boron carbide's structure is only approximately reflected in its formula of B4C, and it shows a clear depletion of carbon from this suggested stoichiometric ratio. This is due to its very complex structure. The substance can be seen with empirical formula B12C3 (i.e., with B12 dodecahedra being a motif), but with less carbon, as the suggested C3 units are replaced with C-B-C chains, and some smaller (B6) octahedra are present as well (see the boron carbide article for structural analysis). The repeating polymer plus semi-crystalline structure of boron carbide gives it great structural strength per weight.
Borides
Binary metal-boron compounds, the metal borides, contain only boron and a metal. They are metallic, very hard, with high melting points. TiB2, ZrB2, and HfB2 have melting points above 3000 °C. Some metal borides find specialized applications as hard materials for cutting tools.
Occurrence
Boron is rare in the Universe and solar system. The amount of boron formed in the Big Bang is negligible. Boron is not generated in the normal course of stellar nucleosynthesis and is destroyed in stellar interiors.
In the high oxygen environment of the Earth's surface, boron is always found fully oxidized to borate. Boron does not appear on Earth in elemental form. Extremely small traces of elemental boron were detected in Lunar regolith.
Although boron is a relatively rare element in the Earth's crust, representing only 0.001% of the crust mass, it can be highly concentrated by the action of water, in which many borates are soluble. It is found naturally combined in compounds such as borax and boric acid (sometimes found in volcanic spring waters). About a hundred borate minerals are known.
Production | Boron | Wikipedia | 445 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Economically important sources of boron are the minerals colemanite, rasorite (kernite), ulexite and tincal. Together these constitute 90% of mined boron-containing ore. The largest global borax deposits known, many still untapped, are in Central and Western Turkey, including the provinces of Eskişehir, Kütahya and Balıkesir. Global proven boron mineral mining reserves exceed one billion metric tonnes, against a yearly production of about four million tonnes.
Turkey and the United States are the largest producers of boron products. Turkey produces about half of the global yearly demand, through Eti Mine Works () a Turkish state-owned mining and chemicals company focusing on boron products. It holds a government monopoly on the mining of borate minerals in Turkey, which possesses 72% of the world's known deposits. In 2012, it held a 47% share of production of global borate minerals, ahead of its main competitor, Rio Tinto Group.
Almost a quarter (23%) of global boron production comes from the Rio Tinto Borax Mine (also known as the U.S. Borax Boron Mine) near Boron, California.
Market trend
The average cost of crystalline elemental boron is US$5/g. Elemental boron is chiefly used in making boron fibers, where it is deposited by chemical vapor deposition on a tungsten core (see below). Boron fibers are used in lightweight composite applications, such as high strength tapes. This use is a very small fraction of total boron use. Boron is introduced into semiconductors as boron compounds, by ion implantation.
Estimated global consumption of boron (almost entirely as boron compounds) was about 4 million tonnes of B2O3 in 2012. As compounds such as borax and kernite its cost was US$377/tonne in 2019. | Boron | Wikipedia | 391 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Increasing demand for boric acid has led a number of producers to invest in additional capacity. Turkey's state-owned Eti Mine Works opened a new boric acid plant with the production capacity of 100,000 tonnes per year at Emet in 2003. Rio Tinto Group increased the capacity of its boron plant from 260,000 tonnes per year in 2003 to 310,000 tonnes per year by May 2005, with plans to grow this to 366,000 tonnes per year in 2006. Chinese boron producers have been unable to meet rapidly growing demand for high quality borates. This has led to imports of sodium tetraborate (borax) growing by a hundredfold between 2000 and 2005 and boric acid imports increasing by 28% per year over the same period.
The rise in global demand has been driven by high growth rates in glass fiber, fiberglass and borosilicate glassware production. A rapid increase in the manufacture of reinforcement-grade boron-containing fiberglass in Asia, has offset the development of boron-free reinforcement-grade fiberglass in Europe and the US. The recent rises in energy prices may lead to greater use of insulation-grade fiberglass, with consequent growth in the boron consumption. Roskill Consulting Group forecasts that world demand for boron will grow by 3.4% per year to reach 21 million tonnes by 2010. The highest growth in demand is expected to be in Asia where demand could rise by an average 5.7% per year.
Applications
Nearly all boron ore extracted from the Earth is refined as boric acid and sodium tetraborate pentahydrate. In the United States, 70% of the boron is used for the production of glass and ceramics.
The major global industrial-scale use of boron compounds (about 46% of end-use) is in production of glass fiber for boron-containing insulating and structural fiberglasses, especially in Asia. Boron is added to the glass as borax pentahydrate or boron oxide, to influence the strength or fluxing qualities of the glass fibers. Another 10% of global boron production is for borosilicate glass as used in high strength glassware. About 15% of global boron is used in boron ceramics, including super-hard materials discussed below. Agriculture consumes 11% of global boron production, and bleaches and detergents about 6%.
Boronated fiberglass | Boron | Wikipedia | 508 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Fiberglasses, a fiber reinforced polymer sometimes contain borosilicate, borax, or boron oxide, and is added to increase the strength of the glass. The highly boronated glasses, E-glass (named for "Electrical" use) are alumino-borosilicate glass. Another common high-boron glasses, C-glass, also has a high boron oxide content, used for glass staple fibers and insulation. D-glass, a borosilicate glass, named for its low dielectric constant.
Because of the ubiquitous use of fiberglass in construction and insulation, boron-containing fiberglasses consume over half the global production of boron, and are the single largest commercial boron market.
Borosilicate glass
Borosilicate glass, which is typically 12–15% B2O3, 80% SiO2, and 2% Al2O3, has a low coefficient of thermal expansion, giving it a good resistance to thermal shock. Schott AG's "Duran" and Owens-Corning's trademarked Pyrex are two major brand names for this glass, used both in laboratory glassware and in consumer cookware and bakeware, chiefly for this resistance.
Elemental boron fiber
Boron fibers (boron filaments) are high-strength, lightweight materials that are used chiefly for advanced aerospace structures as a component of composite materials, as well as limited production consumer and sporting goods such as golf clubs and fishing rods. The fibers can be produced by chemical vapor deposition of boron on a tungsten filament.
Boron fibers and sub-millimeter sized crystalline boron springs are produced by laser-assisted chemical vapor deposition. Translation of the focused laser beam allows production of even complex helical structures. Such structures show good mechanical properties (elastic modulus 450 GPa, fracture strain 3.7%, fracture stress 17 GPa) and can be applied as reinforcement of ceramics or in micromechanical systems.
Boron carbide ceramic
Boron carbide's ability to absorb neutrons without forming long-lived radionuclides (especially when doped with extra boron-10) makes the material attractive as an absorbent for neutron radiation arising in nuclear power plants. Nuclear applications of boron carbide include shielding, control rods and shut-down pellets. Within control rods, boron carbide is often powdered, to increase its surface area. | Boron | Wikipedia | 510 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
High-hardness and abrasive compounds
Boron carbide and cubic boron nitride powders are widely used as abrasives. Boron nitride is a material isoelectronic to carbon. Similar to carbon, it has both hexagonal (soft graphite-like h-BN) and cubic (hard, diamond-like c-BN) forms. h-BN is used as a high temperature component and lubricant. c-BN, also known under commercial name borazon, is a superior abrasive. Its hardness is only slightly smaller than, but its chemical stability is superior, to that of diamond. Heterodiamond (also called BCN) is another diamond-like boron compound.
Metallurgy
Boron is added to boron steels at the level of a few parts per million to increase hardenability. Higher percentages are added to steels used in the nuclear industry due to boron's neutron absorption ability.
Boron can also increase the surface hardness of steels and alloys through boriding. Additionally metal borides are used for coating tools through chemical vapor deposition or physical vapor deposition. Implantation of boron ions into metals and alloys, through ion implantation or ion beam deposition, results in a spectacular increase in surface resistance and microhardness. Laser alloying has also been successfully used for the same purpose. These borides are an alternative to diamond coated tools, and their (treated) surfaces have similar properties to those of the bulk boride.
For example, rhenium diboride can be produced at ambient pressures, but is rather expensive because of rhenium. The hardness of ReB2 exhibits considerable anisotropy because of its hexagonal layered structure. Its value is comparable to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride. Similarly, AlMgB14 + TiB2 composites possess high hardness and wear resistance and are used in either bulk form or as coatings for components exposed to high temperatures and wear loads.
Detergent formulations and bleaching agents
Borax is used in various household laundry and cleaning products. It is also present in some tooth bleaching formulas. | Boron | Wikipedia | 466 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Sodium perborate serves as a source of active oxygen in many detergents, laundry detergents, cleaning products, and laundry bleaches. However, despite its name, "Borateem" laundry bleach no longer contains any boron compounds, using sodium percarbonate instead as a bleaching agent.
Insecticides and antifungals
Zinc borates and boric acid, popularized as fire retardants, are widely used as wood preservatives and insecticides. Boric acid is also used as a domestic insecticide.
Semiconductors
Boron is a useful dopant for such semiconductors as silicon, germanium, and silicon carbide. Having one fewer valence electron than the host atom, it donates a hole resulting in p-type conductivity. Traditional method of introducing boron into semiconductors is via its atomic diffusion at high temperatures. This process uses either solid (B2O3), liquid (BBr3), or gaseous boron sources (B2H6 or BF3). However, after the 1970s, it was mostly replaced by ion implantation, which relies mostly on BF3 as a boron source. Boron trichloride gas is also an important chemical in semiconductor industry, however, not for doping but rather for plasma etching of metals and their oxides. Triethylborane is also injected into vapor deposition reactors as a boron source. Examples are the plasma deposition of boron-containing hard carbon films, silicon nitride–boron nitride films, and for doping of diamond film with boron.
Magnets
Boron is a component of neodymium magnets (Nd2Fe14B), which are among the strongest type of permanent magnet. These magnets are found in a variety of electromechanical and electronic devices, such as magnetic resonance imaging (MRI) medical imaging systems, in compact and relatively small motors and actuators. As examples, computer HDDs (hard disk drives), CD (compact disk) and DVD (digital versatile disk) players rely on neodymium magnet motors to deliver intense rotary power in a remarkably compact package. In mobile phones 'Neo' magnets provide the magnetic field which allows tiny speakers to deliver appreciable audio power.
Shielding and neutron absorber in nuclear reactors
Boron shielding is used as a control for nuclear reactors, taking advantage of its high cross-section for neutron capture. | Boron | Wikipedia | 505 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
In pressurized water reactors a variable concentration of boronic acid in the cooling water is used as a neutron poison to compensate the variable reactivity of the fuel. When new rods are inserted the concentration of boronic acid is maximal, and is reduced during the lifetime.
Other nonmedical uses
Because of its distinctive green flame, amorphous boron is used in pyrotechnic flares.
Some anti-corrosion systems contain borax.
Sodium borates are used as a flux for soldering silver and gold and with ammonium chloride for welding ferrous metals. They are also fire retarding additives to plastics and rubber articles.
Boric acid (also known as orthoboric acid) H3BO3 is used in the production of textile fiberglass and flat panel displays and in many PVAc- and PVOH-based adhesives.
Triethylborane is a substance which ignites the JP-7 fuel of the Pratt & Whitney J58 turbojet/ramjet engines powering the Lockheed SR-71 Blackbird. It was also used to ignite the F-1 Engines on the Saturn V Rocket utilized by NASA's Apollo and Skylab programs from 1967 until 1973. Today SpaceX uses it to ignite the engines on their Falcon 9 rocket. Triethylborane is suitable for this because of its pyrophoric properties, especially the fact that it burns with a very high temperature. Triethylborane is an industrial initiator in radical reactions, where it is effective even at low temperatures.
Borates are used as environmentally benign wood preservatives.
Pharmaceutical and biological applications
Boron plays a role in pharmaceutical and biological applications as it is found in various antibiotics produced by bacteria, such as boromycins, aplasmomycins, borophycins, and tartrolons. These antibiotics have shown inhibitory effects on the growth of certain bacteria, fungi, and protozoa. Boron is also being studied for its potential medicinal applications, including its incorporation into biologically active molecules for therapies like boron neutron capture therapy for brain tumors. Some boron-containing biomolecules may act as signaling molecules interacting with cell surfaces, suggesting a role in cellular communication. | Boron | Wikipedia | 468 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Boric acid has antiseptic, antifungal, and antiviral properties and, for these reasons, is applied as a water clarifier in swimming pool water treatment. Mild solutions of boric acid have been used as eye antiseptics.
Bortezomib (marketed as Velcade and Cytomib). Boron appears as an active element in the organic pharmaceutical bortezomib, a new class of drug called the proteasome inhibitor, for treating myeloma and one form of lymphoma (it is currently in experimental trials against other types of lymphoma). The boron atom in bortezomib binds the catalytic site of the 26S proteasome with high affinity and specificity.
A number of potential boronated pharmaceuticals using boron-10, have been prepared for use in boron neutron capture therapy (BNCT).
Some boron compounds show promise in treating arthritis, though none have as yet been generally approved for the purpose.
Tavaborole (marketed as Kerydin) is an Aminoacyl tRNA synthetase inhibitor which is used to treat toenail fungus. It gained FDA approval in July 2014.
Dioxaborolane chemistry enables radioactive fluoride (18F) labeling of antibodies or red blood cells, which allows for positron emission tomography (PET) imaging of cancer and hemorrhages, respectively. A Human-Derived, Genetic, Positron-emitting and Fluorescent (HD-GPF) reporter system uses a human protein, PSMA and non-immunogenic, and a small molecule that is positron-emitting (boron bound 18F) and fluorescence for dual modality PET and fluorescent imaging of genome modified cells, e.g. cancer, CRISPR/Cas9, or CAR T-cells, in an entire mouse. The dual-modality small molecule targeting PSMA was tested in humans and found the location of primary and metastatic prostate cancer, fluorescence-guided removal of cancer, and detects single cancer cells in tissue margins.
Research | Boron | Wikipedia | 436 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
MgB2
Magnesium diboride (MgB2) is a superconductor with the transition temperature of 39 K. MgB2 wires are produced with the powder-in-tube process and applied in superconducting magnets. A project at CERN to make MgB2 cables has resulted in superconducting test cables able to carry 20,000 amperes for extremely high current distribution applications, such as the contemplated high luminosity version of the Large Hadron Collider.
Commercial isotope enrichment
Because of its high neutron cross-section, boron-10 is often used to control fission in nuclear reactors as a neutron-capturing substance. Several industrial-scale enrichment processes have been developed; however, only the fractionated vacuum distillation of the dimethyl ether adduct of boron trifluoride (DME-BF3) and column chromatography of borates are being used.
Radiation-hardened semiconductors
Cosmic radiation will produce secondary neutrons if it hits spacecraft structures. Those neutrons will be captured in 10B, if it is present in the spacecraft's semiconductors, producing a gamma ray, an alpha particle, and a lithium ion. Those resultant decay products may then irradiate nearby semiconductor "chip" structures, causing data loss (bit flipping, or single event upset). In radiation-hardened semiconductor designs, one countermeasure is to use depleted boron, which is greatly enriched in 11B and contains almost no 10B. This is useful because 11B is largely immune to radiation damage. Depleted boron is a byproduct of the nuclear industry (see above).
Proton-boron fusion
11B is also a candidate as a fuel for aneutronic fusion. When struck by a proton with energy of about 500 keV, it produces three alpha particles and 8.7 MeV of energy. Most other fusion reactions involving hydrogen and helium produce penetrating neutron radiation, which weakens reactor structures and induces long-term radioactivity, thereby endangering operating personnel. The alpha particles from 11B fusion can be turned directly into electric power, and all radiation stops as soon as the reactor is turned off.
Enriched boron (boron-10) | Boron | Wikipedia | 458 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
The 10B isotope is useful for capturing thermal neutrons (see neutron cross section#Typical cross sections). The nuclear industry enriches natural boron to nearly pure 10B. The less-valuable by-product, depleted boron, is nearly pure 11B.
Enriched boron or 10B is used in both radiation shielding and is the primary nuclide used in neutron capture therapy of cancer. In the latter ("boron neutron capture therapy" or BNCT), a compound containing 10B is incorporated into a pharmaceutical which is selectively taken up by a malignant tumor and tissues near it. The patient is then treated with a beam of low energy neutrons at a relatively low neutron radiation dose. The neutrons, however, trigger energetic and short-range secondary alpha particle and lithium-7 heavy ion radiation that are products of the boron-neutron nuclear reaction, and this ion radiation additionally bombards the tumor, especially from inside the tumor cells.
In nuclear reactors, 10B is used for reactivity control and in emergency shutdown systems. It can serve either function in the form of borosilicate control rods or as boric acid. In pressurized water reactors, 10B boric acid is added to the reactor coolant after the plant is shut down for refueling. When the plant is started up again, the boric acid is slowly filtered out over many months as fissile material is used up and the fuel becomes less reactive.
Nuclear fusion
Boron has been investigated for possible applications in nuclear fusion research. It is commonly used for conditioning the walls in fusion reactors by depositing boron coatings on plasma-facing components and walls to reduce the release of hydrogen and impurities from the surfaces. It is also being used for the dissipation of energy in the fusion plasma boundary to suppress excessive energy bursts and heat fluxes to the walls. | Boron | Wikipedia | 381 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Neutron capture therapy
In neutron capture therapy (BNCT) for malignant brain tumors, boron is researched to be used for selectively targeting and destroying tumor cells. The goal is to deliver higher concentrations of the non-radioactive boron isotope (10B) to the tumor cells than to the surrounding normal tissues. When these 10B-containing cells are irradiated with low-energy thermal neutrons, they undergo nuclear capture reactions, releasing high linear energy transfer (LET) particles such as α-particles and lithium-7 nuclei within a limited path length. These high-LET particles can destroy the adjacent tumor cells without causing significant harm to nearby normal cells. Boron acts as a selective agent due to its ability to absorb thermal neutrons and produce short-range physical effects primarily affecting the targeted tissue region. This binary approach allows for precise tumor cell killing while sparing healthy tissues. The effective delivery of boron involves administering boron compounds or carriers capable of accumulating selectively in tumor cells compared to surrounding tissue. BSH and BPA have been used clinically, but research continues to identify more optimal carriers. Accelerator-based neutron sources have also been developed recently as an alternative to reactor-based sources, leading to improved efficiency and enhanced clinical outcomes in BNCT. By employing the properties of boron isotopes and targeted irradiation techniques, BNCT offers a potential approach to treating malignant brain tumors by selectively killing cancer cells while minimizing the damage caused by traditional radiation therapies.
BNCT has shown promising results in clinical trials for various other malignancies, including glioblastoma, head and neck cancer, cutaneous melanoma, hepatocellular carcinoma, lung cancer, and extramammary Paget's disease. The treatment involves a nuclear reaction between nonradioactive boron-10 isotope and low-energy thermal or high-energy epithermal neutrons to generate α particles and lithium nuclei that selectively destroy DNA in tumor cells. The primary challenge lies in developing efficient boron agents with higher content and specific targeting properties tailored for BNCT. Integration of tumor-targeting strategies with BNCT could potentially establish it as a practical personalized treatment option for different types of cancers. Ongoing research explores new boron compounds, optimization strategies, theranostic agents, and radiobiological advances to overcome limitations and cost-effectively improve patient outcomes.
Biological role | Boron | Wikipedia | 490 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Boron is an essential plant nutrient, required primarily for maintaining the integrity of cell walls. However, high soil concentrations of greater than 1.0 ppm lead to marginal and tip necrosis in leaves as well as poor overall growth performance. Levels as low as 0.8 ppm produce these same symptoms in plants that are particularly sensitive to boron in the soil. Nearly all plants, even those somewhat tolerant of soil boron, will show at least some symptoms of boron toxicity when soil boron content is greater than 1.8 ppm. When this content exceeds 2.0 ppm, few plants will perform well and some may not survive.
Some boron-containing antibiotics exist in nature. The first one found was boromycin, isolated from streptomyces in the 1960s. Others are tartrolons, a group of antibiotics discovered in the 1990s from culture broth of the myxobacterium Sorangium cellulosum.
In 2013, chemist and synthetic biologist Steve Benner suggested that the conditions on Mars three billion years ago were much more favorable to the stability of RNA and formation of oxygen-containing boron and molybdenum catalysts found in life. According to Benner's theory, primitive life, which is widely believed to have originated from RNA, first formed on Mars before migrating to Earth.
In human health
It is thought that boron plays several essential roles in animals, including humans, but the exact physiological role is poorly understood. Boron deficiency has only been clearly established in livestock; in humans, boron deficiency may affect bone mineral density, though it has been noted that additional research on the effects of bone health is necessary.
Boron is not classified as an essential human nutrient because research has not established a clear biological function for it. The U.S. Food and Nutrition Board (FNB) found the existing data insufficient to derive a Recommended Dietary Allowance (RDA), Adequate Intake (AI), or Estimated Average Requirement (EAR) for boron and the U.S. Food and Drug Administration (FDA) has not established a daily value for boron for food and dietary supplement labeling purposes. While low boron status can be detrimental to health, probably increasing the risk of osteoporosis, poor immune function, and cognitive decline, high boron levels are associated with cell damage and toxicity. | Boron | Wikipedia | 483 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Still, studies suggest that boron may exert beneficial effects on reproduction and development, calcium metabolism, bone formation, brain function, insulin and energy substrate metabolism, immunity, and steroid hormone (including estrogen) and vitamin D function, among other functions. A small human trial published in 1987 reported on postmenopausal women first made boron deficient and then repleted with 3 mg/day. Boron supplementation markedly reduced urinary calcium excretion and elevated the serum concentrations of 17 beta-estradiol and testosterone. Environmental boron appears to be inversely correlated with arthritis.
The exact mechanism by which boron exerts its physiological effects is not fully understood, but may involve interactions with adenosine monophosphate (ADP) and S-adenosyl methionine (SAM-e), two compounds involved in important cellular functions. Furthermore, boron appears to inhibit cyclic ADP-ribose, thereby affecting the release of calcium ions from the endoplasmic reticulum and affecting various biological processes. Some studies suggest that boron may reduce levels of inflammatory biomarkers. Congenital endothelial dystrophy type 2, a rare form of corneal dystrophy, is linked to mutations in SLC4A11 gene that encodes a transporter reportedly regulating the intracellular concentration of boron.
In humans, boron is usually consumed with food that contains boron, such as fruits, leafy vegetables, and nuts. Foods that are particularly rich in boron include avocados, dried fruits such as raisins, peanuts, pecans, prune juice, grape juice, wine and chocolate powder. According to 2-day food records from the respondents to the Third National Health and Nutrition Examination Survey (NHANES III), adult dietary intake was recorded at 0.9 to 1.4 mg/day.
Health issues and toxicity | Boron | Wikipedia | 393 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Elemental boron, boron oxide, boric acid, borates, and many organoboron compounds are relatively nontoxic to humans and animals (with toxicity similar to that of table salt). The LD50 (dose at which there is 50% mortality) for animals is about 6 g per kg of body weight. Substances with an LD50 above 2 g/kg are considered nontoxic. An intake of 4 g/day of boric acid was reported without incident, but more than this is considered toxic in more than a few doses. Intakes of more than 0.5 grams per day for 50 days cause minor digestive and other problems suggestive of toxicity.
Boric acid is more toxic to insects than to mammals, and is routinely used as an insecticide. However, it has been used in neutron capture therapy alongside other boron compounds such as sodium borocaptate and boronophenylalanine with reported low toxicity levels.
The boranes (boron hydrogen compounds) and similar gaseous compounds are quite poisonous. As usual, boron is not an element that is intrinsically poisonous, but the toxicity of these compounds depends on structure (for another example of this phenomenon, see phosphine). The boranes are also highly flammable and require special care when handling, some combinations of boranes and other compounds are highly explosive. Sodium borohydride presents a fire hazard owing to its reducing nature and the liberation of hydrogen on contact with acid. Boron halides are corrosive.
Boron is necessary for plant growth, but an excess of boron is toxic to plants, and occurs particularly in acidic soil. It presents as a yellowing from the tip inwards of the oldest leaves and black spots in barley leaves, but it can be confused with other stresses such as magnesium deficiency in other plants. | Boron | Wikipedia | 383 | 3755 | https://en.wikipedia.org/wiki/Boron | Physical sciences | Chemical elements_2 | null |
Bromine is a chemical element; it has symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between those of chlorine and iodine. Isolated independently by two chemists, Carl Jacob Löwig (in 1825) and Antoine Jérôme Balard (in 1826), its name was derived , referring to its sharp and pungent smell.
Elemental bromine is very reactive and thus does not occur as a free element in nature. Instead, it can be isolated from colourless soluble crystalline mineral halide salts analogous to table salt, a property it shares with the other halogens. While it is rather rare in the Earth's crust, the high solubility of the bromide ion (Br) has caused its accumulation in the oceans. Commercially the element is easily extracted from brine evaporation ponds, mostly in the United States and Israel. The mass of bromine in the oceans is about one three-hundredth that of chlorine.
At standard conditions for temperature and pressure it is a liquid; the only other element that is liquid under these conditions is mercury. At high temperatures, organobromine compounds readily dissociate to yield free bromine atoms, a process that stops free radical chemical chain reactions. This effect makes organobromine compounds useful as fire retardants, and more than half the bromine produced worldwide each year is put to this purpose. The same property causes ultraviolet sunlight to dissociate volatile organobromine compounds in the atmosphere to yield free bromine atoms, causing ozone depletion. As a result, many organobromine compounds—such as the pesticide methyl bromide—are no longer used. Bromine compounds are still used in well drilling fluids, in photographic film, and as an intermediate in the manufacture of organic chemicals. | Bromine | Wikipedia | 390 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Large amounts of bromide salts are toxic from the action of soluble bromide ions, causing bromism. However, bromine is beneficial for human eosinophils, and is an essential trace element for collagen development in all animals. Hundreds of known organobromine compounds are generated by terrestrial and marine plants and animals, and some serve important biological roles. As a pharmaceutical, the simple bromide ion (Br) has inhibitory effects on the central nervous system, and bromide salts were once a major medical sedative, before replacement by shorter-acting drugs. They retain niche uses as antiepileptics.
History
Bromine was discovered independently by two chemists, Carl Jacob Löwig and Antoine Balard, in 1825 and 1826, respectively.
Löwig isolated bromine from a mineral water spring from his hometown Bad Kreuznach in 1825. Löwig used a solution of the mineral salt saturated with chlorine and extracted the bromine with diethyl ether. After evaporation of the ether, a brown liquid remained. With this liquid as a sample of his work he applied for a position in the laboratory of Leopold Gmelin in Heidelberg. The publication of the results was delayed and Balard published his results first.
Balard found bromine chemicals in the ash of seaweed from the salt marshes of Montpellier. The seaweed was used to produce iodine, but also contained bromine. Balard distilled the bromine from a solution of seaweed ash saturated with chlorine. The properties of the resulting substance were intermediate between those of chlorine and iodine; thus he tried to prove that the substance was iodine monochloride (ICl), but after failing to do so he was sure that he had found a new element and named it muride, derived from the Latin word ("brine"). | Bromine | Wikipedia | 382 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
After the French chemists Louis Nicolas Vauquelin, Louis Jacques Thénard, and Joseph-Louis Gay-Lussac approved the experiments of the young pharmacist Balard, the results were presented at a lecture of the Académie des Sciences and published in Annales de Chimie et Physique. In his publication, Balard stated that he changed the name from muride to brôme on the proposal of M. Anglada. The name brôme (bromine) derives from the Greek (, "stench"). Other sources claim that the French chemist and physicist Joseph-Louis Gay-Lussac suggested the name brôme for the characteristic smell of the vapors. Bromine was not produced in large quantities until 1858, when the discovery of salt deposits in Stassfurt enabled its production as a by-product of potash.
Apart from some minor medical applications, the first commercial use was the daguerreotype. In 1840, bromine was discovered to have some advantages over the previously used iodine vapor to create the light sensitive silver halide layer in daguerreotypy.
By 1864, a 25% solution of liquid bromine in .75 molar aqueous potassium bromide was widely used to treat gangrene during the American Civil War, before the publications of Joseph Lister and Pasteur.
Potassium bromide and sodium bromide were used as anticonvulsants and sedatives in the late 19th and early 20th centuries, but were gradually superseded by chloral hydrate and then by the barbiturates. In the early years of the First World War, bromine compounds such as xylyl bromide were used as poison gas. | Bromine | Wikipedia | 348 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Properties
Bromine is the third halogen, being a nonmetal in group 17 of the periodic table. Its properties are thus similar to those of fluorine, chlorine, and iodine, and tend to be intermediate between those of chlorine and iodine, the two neighbouring halogens. Bromine has the electron configuration [Ar]4s3d4p, with the seven electrons in the fourth and outermost shell acting as its valence electrons. Like all halogens, it is thus one electron short of a full octet, and is hence a strong oxidising agent, reacting with many elements in order to complete its outer shell. Corresponding to periodic trends, it is intermediate in electronegativity between chlorine and iodine (F: 3.98, Cl: 3.16, Br: 2.96, I: 2.66), and is less reactive than chlorine and more reactive than iodine. It is also a weaker oxidising agent than chlorine, but a stronger one than iodine. Conversely, the bromide ion is a weaker reducing agent than iodide, but a stronger one than chloride. These similarities led to chlorine, bromine, and iodine together being classified as one of the original triads of Johann Wolfgang Döbereiner, whose work foreshadowed the periodic law for chemical elements. It is intermediate in atomic radius between chlorine and iodine, and this leads to many of its atomic properties being similarly intermediate in value between chlorine and iodine, such as first ionisation energy, electron affinity, enthalpy of dissociation of the X molecule (X = Cl, Br, I), ionic radius, and X–X bond length. The volatility of bromine accentuates its very penetrating, choking, and unpleasant odour. | Bromine | Wikipedia | 385 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
All four stable halogens experience intermolecular van der Waals forces of attraction, and their strength increases together with the number of electrons among all homonuclear diatomic halogen molecules. Thus, the melting and boiling points of bromine are intermediate between those of chlorine and iodine. As a result of the increasing molecular weight of the halogens down the group, the density and heats of fusion and vaporisation of bromine are again intermediate between those of chlorine and iodine, although all their heats of vaporisation are fairly low (leading to high volatility) thanks to their diatomic molecular structure. The halogens darken in colour as the group is descended: fluorine is a very pale yellow gas, chlorine is greenish-yellow, and bromine is a reddish-brown volatile liquid that freezes at −7.2 °C and boils at 58.8 °C. (Iodine is a shiny black solid.) This trend occurs because the wavelengths of visible light absorbed by the halogens increase down the group. Specifically, the colour of a halogen, such as bromine, results from the electron transition between the highest occupied antibonding π molecular orbital and the lowest vacant antibonding σ molecular orbital. The colour fades at low temperatures so that solid bromine at −195 °C is pale yellow.
Liquid bromine is infrared-transparent.
Like solid chlorine and iodine, solid bromine crystallises in the orthorhombic crystal system, in a layered arrangement of Br molecules. The Br–Br distance is 227 pm (close to the gaseous Br–Br distance of 228 pm) and the Br···Br distance between molecules is 331 pm within a layer and 399 pm between layers (compare the van der Waals radius of bromine, 195 pm). This structure means that bromine is a very poor conductor of electricity, with a conductivity of around 5 × 10 Ω cm just below the melting point, although this is higher than the essentially undetectable conductivity of chlorine.
At a pressure of 55 GPa (roughly 540,000 times atmospheric pressure) bromine undergoes an insulator-to-metal transition. At 75 GPa it changes to a face-centered orthorhombic structure. At 100 GPa it changes to a body centered orthorhombic monatomic form.
Isotopes | Bromine | Wikipedia | 493 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Bromine has two stable isotopes, Br and Br. These are its only two natural isotopes, with Br making up 51% of natural bromine and Br making up the remaining 49%. Both have nuclear spin 3/2− and thus may be used for nuclear magnetic resonance, although Br is more favourable. The relatively 1:1 distribution of the two isotopes in nature is helpful in identification of bromine containing compounds using mass spectroscopy. Other bromine isotopes are all radioactive, with half-lives too short to occur in nature. Of these, the most important are Br (t = 17.7 min), Br (t = 4.421 h), and Br (t = 35.28 h), which may be produced from the neutron activation of natural bromine. The most stable bromine radioisotope is Br (t = 57.04 h). The primary decay mode of isotopes lighter than Br is electron capture to isotopes of selenium; that of isotopes heavier than Br is beta decay to isotopes of krypton; and Br may decay by either mode to stable Se or Kr. Br isotopes from 87Br and heavier undergo beta decay with neutron emission and are of practical importance because they are fission products.
Chemistry and compounds
Bromine is intermediate in reactivity between chlorine and iodine, and is one of the most reactive elements. Bond energies to bromine tend to be lower than those to chlorine but higher than those to iodine, and bromine is a weaker oxidising agent than chlorine but a stronger one than iodine. This can be seen from the standard electrode potentials of the X/X couples (F, +2.866 V; Cl, +1.395 V; Br, +1.087 V; I, +0.615 V; At, approximately +0.3 V). Bromination often leads to higher oxidation states than iodination but lower or equal oxidation states to chlorination. Bromine tends to react with compounds including M–M, M–H, or M–C bonds to form M–Br bonds. | Bromine | Wikipedia | 445 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Hydrogen bromide
The simplest compound of bromine is hydrogen bromide, HBr. It is mainly used in the production of inorganic bromides and alkyl bromides, and as a catalyst for many reactions in organic chemistry. Industrially, it is mainly produced by the reaction of hydrogen gas with bromine gas at 200–400 °C with a platinum catalyst. However, reduction of bromine with red phosphorus is a more practical way to produce hydrogen bromide in the laboratory:
2 P + 6 HO + 3 Br → 6 HBr + 2 HPO
HPO + HO + Br → 2 HBr + HPO
At room temperature, hydrogen bromide is a colourless gas, like all the hydrogen halides apart from hydrogen fluoride, since hydrogen cannot form strong hydrogen bonds to the large and only mildly electronegative bromine atom; however, weak hydrogen bonding is present in solid crystalline hydrogen bromide at low temperatures, similar to the hydrogen fluoride structure, before disorder begins to prevail as the temperature is raised. Aqueous hydrogen bromide is known as hydrobromic acid, which is a strong acid (pK = −9) because the hydrogen bonds to bromine are too weak to inhibit dissociation. The HBr/HO system also involves many hydrates HBr·nHO for n = 1, 2, 3, 4, and 6, which are essentially salts of bromine anions and hydronium cations. Hydrobromic acid forms an azeotrope with boiling point 124.3 °C at 47.63 g HBr per 100 g solution; thus hydrobromic acid cannot be concentrated beyond this point by distillation. | Bromine | Wikipedia | 344 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Unlike hydrogen fluoride, anhydrous liquid hydrogen bromide is difficult to work with as a solvent, because its boiling point is low, it has a small liquid range, its dielectric constant is low and it does not dissociate appreciably into HBr and ions – the latter, in any case, are much less stable than the bifluoride ions () due to the very weak hydrogen bonding between hydrogen and bromine, though its salts with very large and weakly polarising cations such as Cs and (R = Me, Et, Bu) may still be isolated. Anhydrous hydrogen bromide is a poor solvent, only able to dissolve small molecular compounds such as nitrosyl chloride and phenol, or salts with very low lattice energies such as tetraalkylammonium halides.
Other binary bromides
Nearly all elements in the periodic table form binary bromides. The exceptions are decidedly in the minority and stem in each case from one of three causes: extreme inertness and reluctance to participate in chemical reactions (the noble gases, with the exception of xenon in the very unstable XeBr); extreme nuclear instability hampering chemical investigation before decay and transmutation (many of the heaviest elements beyond bismuth); and having an electronegativity higher than bromine's (oxygen, nitrogen, fluorine, and chlorine), so that the resultant binary compounds are formally not bromides but rather oxides, nitrides, fluorides, or chlorides of bromine. (Nonetheless, nitrogen tribromide is named as a bromide as it is analogous to the other nitrogen trihalides.) | Bromine | Wikipedia | 354 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Bromination of metals with Br tends to yield lower oxidation states than chlorination with Cl when a variety of oxidation states is available. Bromides can be made by reaction of an element or its oxide, hydroxide, or carbonate with hydrobromic acid, and then dehydrated by mildly high temperatures combined with either low pressure or anhydrous hydrogen bromide gas. These methods work best when the bromide product is stable to hydrolysis; otherwise, the possibilities include high-temperature oxidative bromination of the element with bromine or hydrogen bromide, high-temperature bromination of a metal oxide or other halide by bromine, a volatile metal bromide, carbon tetrabromide, or an organic bromide. For example, niobium(V) oxide reacts with carbon tetrabromide at 370 °C to form niobium(V) bromide. Another method is halogen exchange in the presence of excess "halogenating reagent", for example:
FeCl + BBr (excess) → FeBr + BCl
When a lower bromide is wanted, either a higher halide may be reduced using hydrogen or a metal as a reducing agent, or thermal decomposition or disproportionation may be used, as follows:
3 WBr + Al 3 WBr + AlBr
EuBr + H → EuBr + HBr
2 TaBr TaBr + TaBr
Most metal bromides with the metal in low oxidation states (+1 to +3) are ionic. Nonmetals tend to form covalent molecular bromides, as do metals in high oxidation states from +3 and above. Both ionic and covalent bromides are known for metals in oxidation state +3 (e.g. scandium bromide is mostly ionic, but aluminium bromide is not). Silver bromide is very insoluble in water and is thus often used as a qualitative test for bromine. | Bromine | Wikipedia | 407 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Bromine halides
The halogens form many binary, diamagnetic interhalogen compounds with stoichiometries XY, XY, XY, and XY (where X is heavier than Y), and bromine is no exception. Bromine forms a monofluoride and monochloride, as well as a trifluoride and pentafluoride. Some cationic and anionic derivatives are also characterised, such as , , , , and . Apart from these, some pseudohalides are also known, such as cyanogen bromide (BrCN), bromine thiocyanate (BrSCN), and bromine azide (BrN).
The pale-brown bromine monofluoride (BrF) is unstable at room temperature, disproportionating quickly and irreversibly into bromine, bromine trifluoride, and bromine pentafluoride. It thus cannot be obtained pure. It may be synthesised by the direct reaction of the elements, or by the comproportionation of bromine and bromine trifluoride at high temperatures. Bromine monochloride (BrCl), a red-brown gas, quite readily dissociates reversibly into bromine and chlorine at room temperature and thus also cannot be obtained pure, though it can be made by the reversible direct reaction of its elements in the gas phase or in carbon tetrachloride. Bromine monofluoride in ethanol readily leads to the monobromination of the aromatic compounds PhX (para-bromination occurs for X = Me, Bu, OMe, Br; meta-bromination occurs for the deactivating X = –COEt, –CHO, –NO); this is due to heterolytic fission of the Br–F bond, leading to rapid electrophilic bromination by Br. | Bromine | Wikipedia | 410 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
At room temperature, bromine trifluoride (BrF) is a straw-coloured liquid. It may be formed by directly fluorinating bromine at room temperature and is purified through distillation. It reacts violently with water and explodes on contact with flammable materials, but is a less powerful fluorinating reagent than chlorine trifluoride. It reacts vigorously with boron, carbon, silicon, arsenic, antimony, iodine, and sulfur to give fluorides, and will also convert most metals and many metal compounds to fluorides; as such, it is used to oxidise uranium to uranium hexafluoride in the nuclear power industry. Refractory oxides tend to be only partially fluorinated, but here the derivatives KBrF and BrFSbF remain reactive. Bromine trifluoride is a useful nonaqueous ionising solvent, since it readily dissociates to form and and thus conducts electricity.
Bromine pentafluoride (BrF) was first synthesised in 1930. It is produced on a large scale by direct reaction of bromine with excess fluorine at temperatures higher than 150 °C, and on a small scale by the fluorination of potassium bromide at 25 °C. It also reacts violently with water and is a very strong fluorinating agent, although chlorine trifluoride is still stronger.
Polybromine compounds
Although dibromine is a strong oxidising agent with a high first ionisation energy, very strong oxidisers such as peroxydisulfuryl fluoride (SOF) can oxidise it to form the cherry-red cation. A few other bromine cations are known, namely the brown and dark brown . The tribromide anion, , has also been characterised; it is analogous to triiodide.
Bromine oxides and oxoacids | Bromine | Wikipedia | 400 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Bromine oxides are not as well-characterised as chlorine oxides or iodine oxides, as they are all fairly unstable: it was once thought that they could not exist at all. Dibromine monoxide is a dark-brown solid which, while reasonably stable at −60 °C, decomposes at its melting point of −17.5 °C; it is useful in bromination reactions and may be made from the low-temperature decomposition of bromine dioxide in a vacuum. It oxidises iodine to iodine pentoxide and benzene to 1,4-benzoquinone; in alkaline solutions, it gives the hypobromite anion.
So-called "bromine dioxide", a pale yellow crystalline solid, may be better formulated as bromine perbromate, BrOBrO. It is thermally unstable above −40 °C, violently decomposing to its elements at 0 °C. Dibromine trioxide, syn-BrOBrO, is also known; it is the anhydride of hypobromous acid and bromic acid. It is an orange crystalline solid which decomposes above −40 °C; if heated too rapidly, it explodes around 0 °C. A few other unstable radical oxides are also known, as are some poorly characterised oxides, such as dibromine pentoxide, tribromine octoxide, and bromine trioxide.
The four oxoacids, hypobromous acid (HOBr), bromous acid (HOBrO), bromic acid (HOBrO), and perbromic acid (HOBrO), are better studied due to their greater stability, though they are only so in aqueous solution. When bromine dissolves in aqueous solution, the following reactions occur:
{|
|-
| Br + HO || HOBr + H + Br || K = 7.2 × 10 mol l
|-
| Br + 2 OH || OBr + HO + Br || K = 2 × 10 mol l
|}
Hypobromous acid is unstable to disproportionation. The hypobromite ions thus formed disproportionate readily to give bromide and bromate:
{|
|-
| 3 BrO 2 Br + || K = 10
|} | Bromine | Wikipedia | 486 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Bromous acids and bromites are very unstable, although the strontium and barium bromites are known. More important are the bromates, which are prepared on a small scale by oxidation of bromide by aqueous hypochlorite, and are strong oxidising agents. Unlike chlorates, which very slowly disproportionate to chloride and perchlorate, the bromate anion is stable to disproportionation in both acidic and aqueous solutions. Bromic acid is a strong acid. Bromides and bromates may comproportionate to bromine as follows:
+ 5 Br + 6 H → 3 Br + 3 HO
There were many failed attempts to obtain perbromates and perbromic acid, leading to some rationalisations as to why they should not exist, until 1968 when the anion was first synthesised from the radioactive beta decay of unstable . Today, perbromates are produced by the oxidation of alkaline bromate solutions by fluorine gas. Excess bromate and fluoride are precipitated as silver bromate and calcium fluoride, and the perbromic acid solution may be purified. The perbromate ion is fairly inert at room temperature but is thermodynamically extremely oxidising, with extremely strong oxidising agents needed to produce it, such as fluorine or xenon difluoride. The Br–O bond in is fairly weak, which corresponds to the general reluctance of the 4p elements arsenic, selenium, and bromine to attain their group oxidation state, as they come after the scandide contraction characterised by the poor shielding afforded by the radial-nodeless 3d orbitals.
Organobromine compounds
Like the other carbon–halogen bonds, the C–Br bond is a common functional group that forms part of core organic chemistry. Formally, compounds with this functional group may be considered organic derivatives of the bromide anion. Due to the difference of electronegativity between bromine (2.96) and carbon (2.55), the carbon atom in a C–Br bond is electron-deficient and thus electrophilic. The reactivity of organobromine compounds resembles but is intermediate between the reactivity of organochlorine and organoiodine compounds. For many applications, organobromides represent a compromise of reactivity and cost. | Bromine | Wikipedia | 504 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Organobromides are typically produced by additive or substitutive bromination of other organic precursors. Bromine itself can be used, but due to its toxicity and volatility, safer brominating reagents are normally used, such as N-bromosuccinimide. The principal reactions for organobromides include dehydrobromination, Grignard reactions, reductive coupling, and nucleophilic substitution.
Organobromides are the most common organohalides in nature, even though the concentration of bromide is only 0.3% of that for chloride in sea water, because of the easy oxidation of bromide to the equivalent of Br, a potent electrophile. The enzyme bromoperoxidase catalyzes this reaction. The oceans are estimated to release 1–2 million tons of bromoform and 56,000 tons of bromomethane annually.
An old qualitative test for the presence of the alkene functional group is that alkenes turn brown aqueous bromine solutions colourless, forming a bromohydrin with some of the dibromoalkane also produced. The reaction passes through a short-lived strongly electrophilic bromonium intermediate. This is an example of a halogen addition reaction.
Occurrence and production
Bromine is significantly less abundant in the crust than fluorine or chlorine, comprising only 2.5 parts per million of the Earth's crustal rocks, and then only as bromide salts. It is the 46th most abundant element in Earth's crust. It is significantly more abundant in the oceans, resulting from long-term leaching. There, it makes up 65 parts per million, corresponding to a ratio of about one bromine atom for every 660 chlorine atoms. Salt lakes and brine wells may have higher bromine concentrations: for example, the Dead Sea contains 0.4% bromide ions. It is from these sources that bromine extraction is mostly economically feasible. Bromine is the tenth most abundant element in seawater. | Bromine | Wikipedia | 427 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
The main sources of bromine production are Israel and Jordan. The element is liberated by halogen exchange, using chlorine gas to oxidise Br to Br. This is then removed with a blast of steam or air, and is then condensed and purified. Today, bromine is transported in large-capacity metal drums or lead-lined tanks that can hold hundreds of kilograms or even tonnes of bromine. The bromine industry is about one-hundredth the size of the chlorine industry. Laboratory production is unnecessary because bromine is commercially available and has a long shelf life.
Applications
A wide variety of organobromine compounds are used in industry. Some are prepared from bromine and others are prepared from hydrogen bromide, which is obtained by burning hydrogen in bromine.
Flame retardants
Brominated flame retardants represent a commodity of growing importance, and make up the largest commercial use of bromine. When the brominated material burns, the flame retardant produces hydrobromic acid which interferes in the radical chain reaction of the oxidation reaction of the fire. The mechanism is that the highly reactive hydrogen radicals, oxygen radicals, and hydroxyl radicals react with hydrobromic acid to form less reactive bromine radicals (i.e., free bromine atoms). Bromine atoms may also react directly with other radicals to help terminate the free radical chain-reactions that characterise combustion.
To make brominated polymers and plastics, bromine-containing compounds can be incorporated into the polymer during polymerisation. One method is to include a relatively small amount of brominated monomer during the polymerisation process. For example, vinyl bromide can be used in the production of polyethylene, polyvinyl chloride or polypropylene. Specific highly brominated molecules can also be added that participate in the polymerisation process. For example, tetrabromobisphenol A can be added to polyesters or epoxy resins, where it becomes part of the polymer. Epoxies used in printed circuit boards are normally made from such flame retardant resins, indicated by the FR in the abbreviation of the products (FR-4 and FR-2). In some cases, the bromine-containing compound may be added after polymerisation. For example, decabromodiphenyl ether can be added to the final polymers. | Bromine | Wikipedia | 488 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
A number of gaseous or highly volatile brominated halomethane compounds are non-toxic and make superior fire suppressant agents by this same mechanism, and are particularly effective in enclosed spaces such as submarines, airplanes, and spacecraft. However, they are expensive and their production and use has been greatly curtailed due to their effect as ozone-depleting agents. They are no longer used in routine fire extinguishers, but retain niche uses in aerospace and military automatic fire suppression applications. They include bromochloromethane (Halon 1011, CHBrCl), bromochlorodifluoromethane (Halon 1211, CBrClF), and bromotrifluoromethane (Halon 1301, CBrF).
Other uses
Silver bromide is used, either alone or in combination with silver chloride and silver iodide, as the light sensitive constituent of photographic emulsions.
Ethylene bromide was an additive in gasolines containing lead anti-engine knocking agents. It scavenges lead by forming volatile lead bromide, which is exhausted from the engine. This application accounted for 77% of the bromine use in 1966 in the US. This application has declined since the 1970s due to environmental regulations (see below).
Brominated vegetable oil (BVO), a complex mixture of plant-derived triglycerides that have been reacted to contain atoms of the element bromine bonded to the molecules, is used primarily to help emulsify citrus-flavored soft drinks, preventing them from separating during distribution.
Poisonous bromomethane was widely used as pesticide to fumigate soil and to fumigate housing, by the tenting method. Ethylene bromide was similarly used. These volatile organobromine compounds are all now regulated as ozone depletion agents. The Montreal Protocol on Substances that Deplete the Ozone Layer scheduled the phase out for the ozone depleting chemical by 2005, and organobromide pesticides are no longer used (in housing fumigation they have been replaced by such compounds as sulfuryl fluoride, which contain neither the chlorine or bromine organics which harm ozone). Before the Montreal protocol in 1991 (for example) an estimated 35,000 tonnes of the chemical were used to control nematodes, fungi, weeds and other soil-borne diseases. | Bromine | Wikipedia | 490 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
In pharmacology, inorganic bromide compounds, especially potassium bromide, were frequently used as general sedatives in the 19th and early 20th century. Bromides in the form of simple salts are still used as anticonvulsants in both veterinary and human medicine, although the latter use varies from country to country. For example, the U.S. Food and Drug Administration (FDA) does not approve bromide for the treatment of any disease, and sodium bromide was removed from over-the-counter sedative products like Bromo-Seltzer, in 1975. Commercially available organobromine pharmaceuticals include the vasodilator nicergoline, the sedative brotizolam, the anticancer agent pipobroman, and the antiseptic merbromin. Otherwise, organobromine compounds are rarely pharmaceutically useful, in contrast to the situation for organofluorine compounds. Several drugs are produced as the bromide (or equivalents, hydrobromide) salts, but in such cases bromide serves as an innocuous counterion of no biological significance.
Other uses of organobromine compounds include high-density drilling fluids, dyes (such as Tyrian purple and the indicator bromothymol blue), and pharmaceuticals. Bromine itself, as well as some of its compounds, are used in water treatment, and is the precursor of a variety of inorganic compounds with an enormous number of applications (e.g. silver bromide for photography). Zinc–bromine batteries are hybrid flow batteries used for stationary electrical power backup and storage; from household scale to industrial scale.
Bromine is used in cooling towers (in place of chlorine) for controlling bacteria, algae, fungi, and zebra mussels.
Because it has similar antiseptic qualities to chlorine, bromine can be used in the same manner as chlorine as a disinfectant or antimicrobial in applications such as swimming pools. Bromine came into this use in the United States during World War II due to a predicted shortage of chlorine. However, bromine is usually not used outside for these applications due to it being relatively more expensive than chlorine and the absence of a stabilizer to protect it from the sun. For indoor pools, it can be a good option as it is effective at a wider pH range. It is also more stable in a heated pool or hot tub.
Biological role and toxicity | Bromine | Wikipedia | 511 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
A 2014 study suggests that bromine (in the form of bromide ion) is a necessary cofactor in the biosynthesis of collagen IV, making the element essential to basement membrane architecture and tissue development in animals. Nevertheless, no clear deprivation symptoms or syndromes have been documented in mammals. In other biological functions, bromine may be non-essential but still beneficial when it takes the place of chlorine. For example, in the presence of hydrogen peroxide, HO, formed by the eosinophil, and either chloride, iodide, thiocyanate, or bromide ions, eosinophil peroxidase provides a potent mechanism by which eosinophils kill multicellular parasites (such as the nematode worms involved in filariasis) and some bacteria (such as tuberculosis bacteria). Eosinophil peroxidase is a haloperoxidase that preferentially uses bromide over chloride for this purpose, generating hypobromite (hypobromous acid), although the use of chloride is possible.
α-Haloesters are generally thought of as highly reactive and consequently toxic intermediates in organic synthesis. Nevertheless, mammals, including humans, cats, and rats, appear to biosynthesize traces of an α-bromoester, 2-octyl 4-bromo-3-oxobutanoate, which is found in their cerebrospinal fluid and appears to play a yet unclarified role in inducing REM sleep. Neutrophil myeloperoxidase can use HO and Br to brominate deoxycytidine, which could result in DNA mutations. Marine organisms are the main source of organobromine compounds, and it is in these organisms that bromine is more firmly shown to be essential. More than 1600 such organobromine compounds were identified by 1999. The most abundant is methyl bromide (CHBr), of which an estimated 56,000 tonnes is produced by marine algae each year. The essential oil of the Hawaiian alga Asparagopsis taxiformis consists of 80% bromoform. Most of such organobromine compounds in the sea are made by the action of a unique algal enzyme, vanadium bromoperoxidase. | Bromine | Wikipedia | 484 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
The bromide anion is not very toxic: a normal daily intake is 2 to 8 milligrams. However, high levels of bromide chronically impair the membrane of neurons, which progressively impairs neuronal transmission, leading to toxicity, known as bromism. Bromide has an elimination half-life of 9 to 12 days, which can lead to excessive accumulation. Doses of 0.5 to 1 gram per day of bromide can lead to bromism. Historically, the therapeutic dose of bromide is about 3 to 5 grams of bromide, thus explaining why chronic toxicity (bromism) was once so common. While significant and sometimes serious disturbances occur to neurologic, psychiatric, dermatological, and gastrointestinal functions, death from bromism is rare. Bromism is caused by a neurotoxic effect on the brain which results in somnolence, psychosis, seizures and delirium.
Elemental bromine (Br) is toxic and causes chemical burns on human flesh. Inhaling bromine gas results in similar irritation of the respiratory tract, causing coughing, choking, shortness of breath, and death if inhaled in large enough amounts. Chronic exposure may lead to frequent bronchial infections and a general deterioration of health. As a strong oxidising agent, bromine is incompatible with most organic and inorganic compounds. Caution is required when transporting bromine; it is commonly carried in steel tanks lined with lead, supported by strong metal frames. The Occupational Safety and Health Administration (OSHA) of the United States has set a permissible exposure limit (PEL) for bromine at a time-weighted average (TWA) of 0.1 ppm. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of TWA 0.1 ppm and a short-term limit of 0.3 ppm. The exposure to bromine immediately dangerous to life and health (IDLH) is 3 ppm. Bromine is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities. | Bromine | Wikipedia | 480 | 3756 | https://en.wikipedia.org/wiki/Bromine | Physical sciences | Chemical elements_2 | null |
Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.
The most common minerals of barium are barite (barium sulfate, BaSO4) and witherite (barium carbonate, BaCO3). The name barium originates from the alchemical derivative "baryta", from Greek (), meaning 'heavy'. Baric is the adjectival form of barium. Barium was identified as a new element in 1772, but not reduced to a metal until 1808 with the advent of electrolysis.
Barium has few industrial applications. Historically, it was used as a getter for vacuum tubes and in oxide form as the emissive coating on indirectly heated cathodes. It is a component of YBCO (high-temperature superconductors) and electroceramics, and is added to steel and cast iron to reduce the size of carbon grains within the microstructure. Barium compounds are added to fireworks to impart a green color. Barium sulfate is used as an insoluble additive to oil well drilling fluid. In a purer form it is used as X-ray radiocontrast agents for imaging the human gastrointestinal tract. Water-soluble barium compounds are poisonous and have been used as rodenticides.
Characteristics
Physical properties
Barium is a soft, silvery-white metal, with a slight golden shade when ultrapure. The silvery-white color of barium metal rapidly vanishes upon oxidation in air yielding a dark gray layer containing the oxide. Barium has a medium specific weight and high electrical conductivity. Because barium is difficult to purify, many of its properties have not been accurately determined. | Barium | Wikipedia | 393 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
At room temperature and pressure, barium metal adopts a body-centered cubic structure, with a barium–barium distance of 503 picometers, expanding with heating at a rate of approximately 1.8/°C. It is a soft metal with a Mohs hardness of 1.25. Its melting temperature of is intermediate between those of the lighter strontium () and heavier radium (); however, its boiling point of exceeds that of strontium (). The density (3.62 g/cm3) is again intermediate between those of strontium (2.36 g/cm3) and radium (≈5 g/cm3).
Chemical reactivity
Barium is chemically similar to magnesium, calcium, and strontium, but more reactive. Its compounds are almost invariably found in the +2 oxidation state. As expected for a highly electropositive metal, barium's reaction with chalcogens is highly exothermic (release energy). Barium reacts with atmospheric oxygen in air at room temperature. For this reason, metallic barium is often stored under oil or in an inert atmosphere. Reactions with other nonmetals, such as carbon, nitrogen, phosphorus, silicon, and hydrogen, proceed upon heating. Reactions with water and alcohols are also exothermic and release hydrogen gas:
Ba + 2 ROH → Ba(OR)2 + H2↑ (R is an alkyl group or a hydrogen atom)
Barium reacts with ammonia to form the electride [Ba(NH3)6](e−)2, which near room temperature gives the amide Ba(NH2)2.
The metal is readily attacked by acids. Sulfuric acid is a notable exception because passivation stops the reaction by forming the insoluble barium sulfate on the surface. Barium combines with several other metals, including aluminium, zinc, lead, and tin, forming intermetallic phases and alloys.
Compounds
Barium salts are typically white when solid and colorless when dissolved. They are denser than the strontium or calcium analogs, except for the halides (see table; zinc is given for comparison). | Barium | Wikipedia | 454 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
Barium hydroxide ("baryta") was known to alchemists, who produced it by heating barium carbonate. Unlike calcium hydroxide, it absorbs very little CO2 in aqueous solutions and is therefore insensitive to atmospheric fluctuations. This property is used in calibrating pH equipment.
Barium compounds burn with a green to pale green flame, which is an efficient test to detect a barium compound. The color results from spectral lines at 455.4, 493.4, 553.6, and 611.1 nm.
Organobarium compounds are a growing field of knowledge: recently discovered are dialkylbariums and alkylhalobariums.
Isotopes
Barium found in the Earth's crust is a mixture of seven primordial nuclides, barium-130, 132, and 134 through 138. Barium-130 undergoes very slow radioactive decay to xenon-130 by double beta plus decay, with a half-life of (0.5–2.7)×1021 years (about 1011 times the age of the universe). Its abundance is ≈0.1% that of natural barium. Theoretically, barium-132 can similarly undergo double beta decay to xenon-132; this decay has not been detected. The radioactivity of these isotopes is so weak that they pose no danger to life.
Of the stable isotopes, barium-138 composes 71.7% of all barium; other isotopes have decreasing abundance with decreasing mass number.
In total, barium has 40 known isotopes, ranging in mass between 114 and 153. The most stable artificial radioisotope is barium-133 with a half-life of approximately 10.51 years. Five other isotopes have half-lives longer than a day. Barium also has 10 meta states, of which barium-133m1 is the most stable with a half-life of about 39 hours.
History
Alchemists in the early Middle Ages knew about some barium minerals. Smooth pebble-like stones of mineral baryte were found in volcanic rock near Bologna, Italy, and so were called "Bologna stones". Alchemists were attracted to them because after exposure to light they would glow for years. The phosphorescent properties of baryte heated with organics were described by V. Casciorolus in 1602. | Barium | Wikipedia | 501 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
Carl Scheele determined that baryte contained a new element in 1772, but could not isolate barium, only barium oxide. Johan Gottlieb Gahn also isolated barium oxide two years later in similar studies. Oxidized barium was at first called "barote" by Guyton de Morveau, a name that was changed by Antoine Lavoisier to baryte (in French) or baryta (in Latin). Also in the 18th century, English mineralogist William Withering noted a heavy mineral in the lead mines of Cumberland, now known to be witherite. Barium was first isolated by electrolysis of molten barium salts in 1808 by Sir Humphry Davy in England. Davy, by analogy with calcium, named "barium" after baryta, with the "-ium" ending signifying a metallic element. Robert Bunsen and Augustus Matthiessen obtained pure barium by electrolysis of a molten mixture of barium chloride and ammonium chloride.
The production of pure oxygen in the Brin process was a large-scale application of barium peroxide in the 1880s, before it was replaced by electrolysis and fractional distillation of liquefied air in the early 1900s. In this process barium oxide reacts at with air to form barium peroxide, which decomposes above by releasing oxygen:
2 BaO + O2 ⇌ 2 BaO2
Barium sulfate was first applied as a radiocontrast agent in X-ray imaging of the digestive system in 1908.
Occurrence and production
The abundance of barium is 0.0425% in the Earth's crust and 13 μg/L in sea water. The primary commercial source of barium is baryte (also called barytes or heavy spar), a barium sulfate mineral. with deposits in many parts of the world. Another commercial source, far less important than baryte, is witherite, barium carbonate. The main deposits are located in Britain, Romania, and the former USSR. | Barium | Wikipedia | 420 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
The baryte reserves are estimated between 0.7 and 2 billion tonnes. The highest production, 8.3 million tonnes, was achieved in 1981, but only 7–8% was used for barium metal or compounds. Baryte production has risen since the second half of the 1990s from 5.6 million tonnes in 1996 to 7.6 in 2005 and 7.8 in 2011. China accounts for more than 50% of this output, followed by India (14% in 2011), Morocco (8.3%), US (8.2%), Iran and Kazakhstan (2.6% each) and Turkey (2.5%).
The mined ore is washed, crushed, classified, and separated from quartz. If the quartz penetrates too deeply into the ore, or the iron, zinc, or lead content is abnormally high, then froth flotation is used. The product is a 98% pure baryte (by mass); the purity should be no less than 95%, with a minimal content of iron and silicon dioxide. It is then reduced by carbon to barium sulfide:
BaSO4 + 2 C → BaS + 2 CO2
The water-soluble barium sulfide is the starting point for other compounds: treating BaS with oxygen produces the sulfate, with nitric acid the nitrate, with aqueous carbon dioxide the carbonate, and so on. The nitrate can be thermally decomposed to yield the oxide. Barium metal is produced by reduction with aluminium at . The intermetallic compound BaAl4 is produced first:
3 BaO + 14 Al → 3 BaAl4 + Al2O3
BaAl4 is an intermediate reacted with barium oxide to produce the metal. Note that not all barium is reduced.
8 BaO + BaAl4 → Ba↓ + 7 BaAl2O4
The remaining barium oxide reacts with the formed aluminium oxide:
BaO + Al2O3 → BaAl2O4
and the overall reaction is
4 BaO + 2 Al → 3 Ba↓ + BaAl2O4
Barium vapor is condensed and packed into molds in an atmosphere of argon. This method is used commercially, yielding ultrapure barium. Commonly sold barium is about 99% pure, with main impurities being strontium and calcium (up to 0.8% and 0.25%) and other contaminants contributing less than 0.1%. | Barium | Wikipedia | 500 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
A similar reaction with silicon at yields barium and barium metasilicate. Electrolysis is not used because barium readily dissolves in molten halides and the product is rather impure.
Gemstone
The barium mineral, benitoite (barium titanium silicate), occurs as a very rare blue fluorescent gemstone, and is the official state gem of California.
Barium in seawater
Barium exists in seawater as the Ba2+ ion with an average oceanic concentration of 109 nmol/kg. Barium also exists in the ocean as BaSO4, or barite. Barium has a nutrient-like profile with a residence time of 10,000 years.
Barium shows a relatively consistent concentration in upper ocean seawater, excepting regions of high river inputs and regions with strong upwelling. There is little depletion of barium concentrations in the upper ocean for an ion with a nutrient-like profile, thus lateral mixing is important. Barium isotopic values show basin-scale balances instead of local or short-term processes.
Applications
Metal and alloys
Barium, as a metal or when alloyed with aluminium, is used to remove unwanted gases (gettering) from vacuum tubes, such as TV picture tubes. Barium is suitable for this purpose because of its low vapor pressure and reactivity towards oxygen, nitrogen, carbon dioxide, and water; it can even partly remove noble gases by dissolving them in the crystal lattice. This application is gradually disappearing due to the rising popularity of the tubeless LCD, LED, and plasma sets.
Other uses of elemental barium are minor and include an additive to silumin (aluminium–silicon alloys) that refines their structure, as well as
bearing alloys;
lead–tin soldering alloys – to increase the creep resistance;
alloy with nickel for spark plugs;
additive to steel and cast iron as an inoculant;
alloys with calcium, manganese, silicon, and aluminium as high-grade steel deoxidizers.
Barium sulfate and baryte | Barium | Wikipedia | 416 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
Barium sulfate (the mineral baryte, BaSO4) is important to the petroleum industry as a drilling fluid in oil and gas wells. The precipitate of the compound (called "blanc fixe", from the French for "permanent white") is used in paints and varnishes; as a filler in ringing ink, plastics, and rubbers; as a paper coating pigment; and in nanoparticles, to improve physical properties of some polymers, such as epoxies.
Barium sulfate has a low toxicity and relatively high density of ca. 4.5 g/cm3 (and thus opacity to X-rays). For this reason it is used as a radiocontrast agent in X-ray imaging of the digestive system ("barium meals" and "barium enemas"). Lithopone, a pigment that contains barium sulfate and zinc sulfide, is a permanent white with good covering power that does not darken when exposed to sulfides.
Other barium compounds
Other compounds of barium find only niche applications, limited by the toxicity of Ba2+ ions (barium carbonate is a rat poison), which is not a problem for the insoluble BaSO4.
Barium oxide coating on the electrodes of fluorescent lamps facilitates the release of electrons.
By its great atomic density, barium carbonate increases the refractive index and luster of glass and reduces leaks of X-rays from cathode-ray tubes (CRTs) TV sets.
Barium, typically as barium nitrate imparts a yellow or "apple" green color to fireworks; for brilliant green barium chloride is used.
Barium peroxide is a catalyst in the aluminothermic reaction (thermite) for welding rail tracks. It is also a green flare in tracer ammunition and a bleaching agent.
Barium titanate is a promising electroceramic.
Barium fluoride is used for optics in infrared applications because of its wide transparency range of 0.15–12 micrometers.
YBCO was the first high-temperature superconductor cooled by liquid nitrogen, with a transition temperature of greater than the boiling point of nitrogen ().
Ferrite, a type of sintered ceramic composed of iron oxide (Fe2O3) and barium oxide (BaO), is both electrically nonconductive and ferrimagnetic, and can be temporarily or permanently magnetized. | Barium | Wikipedia | 511 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
Palaeoceanography
The lateral mixing of barium is caused by water mass mixing and ocean circulation. Global ocean circulation reveals a strong correlation between dissolved barium and silicic acid. The large-scale ocean circulation combined with remineralization of barium show a similar correlation between dissolved barium and ocean alkalinity.
Dissolved barium's correlation with silicic acid can be seen both vertically and spatially. Particulate barium shows a strong correlation with particulate organic carbon or POC. Barium is becoming more popular as a base for palaeoceanographic proxies. With both dissolved and particulate barium's links with silicic acid and POC, it can be used to determine historical variations in the biological pump, carbon cycle, and global climate.
The barium particulate barite (BaSO4), as one of many proxies, can be used to provide a host of historical information on processes in different oceanic settings (water column, sediments, and hydrothermal sites). In each setting there are differences in isotopic and elemental composition of the barite particulate. Barite in the water column, known as marine or pelagic barite, reveals information on seawater chemistry variation over time. Barite in sediments, known as diagenetic or cold seeps barite, gives information about sedimentary redox processes. Barite formed via hydrothermal activity at hydrothermal vents, known as hydrothermal barite, reveals alterations in the condition of the earth's crust around those vents.
Toxicity
Soluble barium compounds have LD50 near 10 mg/kg (oral rats). Symptoms include "convulsions... paralysis of the peripheral nerve system ... severe inflammation of the gastrointestinal tract". The insoluble sulfate is nontoxic and is not classified as a dangerous goods in transport regulations.
Little is known about the long term effects of barium exposure. The US EPA considers it unlikely that barium is carcinogenic when consumed orally. Inhaled dust containing insoluble barium compounds can accumulate in the lungs, causing a benign condition called baritosis. | Barium | Wikipedia | 444 | 3757 | https://en.wikipedia.org/wiki/Barium | Physical sciences | Chemical elements_2 | null |
Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory) where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.
The major isotope of berkelium, 249Bk, is synthesized in minute quantities in dedicated high-flux nuclear reactors, mainly at the Oak Ridge National Laboratory in Tennessee, United States, and at the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. The longest-lived and second-most important isotope, 247Bk, can be synthesized via irradiation of 244Cm with high-energy alpha particles.
Just over one gram of berkelium has been produced in the United States since 1967. There is no practical application of berkelium outside scientific research which is mostly directed at the synthesis of heavier transuranium elements and superheavy elements. A 22-milligram batch of berkelium-249 was prepared during a 250-day irradiation period and then purified for a further 90 days at Oak Ridge in 2009. This sample was used to synthesize the new element tennessine for the first time in 2009 at the Joint Institute for Nuclear Research, Russia, after it was bombarded with calcium-48 ions for 150 days. This was the culmination of the Russia–US collaboration on the synthesis of the heaviest elements on the periodic table.
Berkelium is a soft, silvery-white, radioactive metal. The berkelium-249 isotope emits low-energy electrons and thus is relatively safe to handle. It decays with a half-life of 330 days to californium-249, which is a strong emitter of ionizing alpha particles. This gradual transformation is an important consideration when studying the properties of elemental berkelium and its chemical compounds, since the formation of californium brings not only chemical contamination, but also free-radical effects and self-heating from the emitted alpha particles.
Characteristics
Physical | Berkelium | Wikipedia | 458 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
Berkelium is a soft, silvery-white, radioactive actinide metal. In the periodic table, it is located to the right of the actinide curium, to the left of the actinide californium and below the lanthanide terbium with which it shares many similarities in physical and chemical properties. Its density of 14.78 g/cm3 lies between those of curium (13.52 g/cm3) and californium (15.1 g/cm3), as does its melting point of 986 °C, below that of curium (1340 °C) but higher than that of californium (900 °C). Berkelium is relatively soft and has one of the lowest bulk moduli among the actinides, at about 20 GPa (2 Pa).
ions shows two sharp fluorescence peaks at 652 nanometers (red light) and 742 nanometers (deep red – near-infrared) due to internal transitions at the f-electron shell. The relative intensity of these peaks depends on the excitation power and temperature of the sample. This emission can be observed, for example, after dispersing berkelium ions in a silicate glass, by melting the glass in presence of berkelium oxide or halide.
Between 70 K and room temperature, berkelium behaves as a Curie–Weiss paramagnetic material with an effective magnetic moment of 9.69 Bohr magnetons (μB) and a Curie temperature of 101 K. This magnetic moment is almost equal to the theoretical value of 9.72 μB calculated within the simple atomic L-S coupling model. Upon cooling to about 34 K, berkelium undergoes a transition to an antiferromagnetic state. The enthalpy of dissolution in hydrochloric acid at standard conditions is −600 kJ/mol, from which the standard enthalpy of formation (ΔfH°) of aqueous ions is obtained as −601 kJ/mol. The standard electrode potential /Bk is −2.01 V. The ionization potential of a neutral berkelium atom is 6.23 eV. | Berkelium | Wikipedia | 459 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
Allotropes
At ambient conditions, berkelium assumes its most stable α form which has a hexagonal symmetry, space group P63/mmc, lattice parameters of 341 pm and 1107 pm. The crystal has a double-hexagonal close packing structure with the layer sequence ABAC and so is isotypic (having a similar structure) with α-lanthanum and α-forms of actinides beyond curium. This crystal structure changes with pressure and temperature. When compressed at room temperature to 7 GPa, α-berkelium transforms to the β modification, which has a face-centered cubic (fcc) symmetry and space group Fmm. This transition occurs without change in volume, but the enthalpy increases by 3.66 kJ/mol. Upon further compression to 25 GPa, berkelium transforms to an orthorhombic γ-berkelium structure similar to that of α-uranium. This transition is accompanied by a 12% volume decrease and delocalization of the electrons at the 5f electron shell. No further phase transitions are observed up to 57 GPa.
Upon heating, α-berkelium transforms into another phase with an fcc lattice (but slightly different from β-berkelium), space group Fmm and the lattice constant of 500 pm; this fcc structure is equivalent to the closest packing with the sequence ABC. This phase is metastable and will gradually revert to the original α-berkelium phase at room temperature. The temperature of the phase transition is believed to be quite close to the melting point. | Berkelium | Wikipedia | 325 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
Chemical
Like all actinides, berkelium dissolves in various aqueous inorganic acids, liberating gaseous hydrogen and converting into the state. This trivalent oxidation state (+3) is the most stable, especially in aqueous solutions, but tetravalent (+4), pentavalent (+5), and possibly divalent (+2) berkelium compounds are also known. The existence of divalent berkelium salts is uncertain and has only been reported in mixed lanthanum(III) chloride-strontium chloride melts. A similar behavior is observed for the lanthanide analogue of berkelium, terbium. Aqueous solutions of ions are green in most acids. The color of ions is yellow in hydrochloric acid and orange-yellow in sulfuric acid. Berkelium does not react rapidly with oxygen at room temperature, possibly due to the formation of a protective oxide layer surface. However, it reacts with molten metals, hydrogen, halogens, chalcogens and pnictogens to form various binary compounds.
Isotopes
Nineteen isotopes and six nuclear isomers (excited states of an isotope) of berkelium have been characterized, with mass numbers ranging from 233 to 253 (except 235 and 237). All of them are radioactive. The longest half-lives are observed for 247Bk (1,380 years), 248Bk (over 300 years), and 249Bk (330 days); the half-lives of the other isotopes range from microseconds to several days. The isotope which is the easiest to synthesize is berkelium-249. This emits mostly soft β-particles which are inconvenient for detection. Its alpha radiation is rather weak (1.45%) with respect to the β-radiation, but is sometimes used to detect this isotope. The second important berkelium isotope, berkelium-247, is an alpha-emitter, as are most actinide isotopes.
Occurrence
All berkelium isotopes have a half-life far too short to be primordial. Therefore, any primordial berkelium − that is, berkelium present on the Earth during its formation − has decayed by now. | Berkelium | Wikipedia | 469 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
On Earth, berkelium is mostly concentrated in certain areas, which were used for the atmospheric nuclear weapons tests between 1945 and 1980, as well as at the sites of nuclear incidents, such as the Chernobyl disaster, Three Mile Island accident and 1968 Thule Air Base B-52 crash. Analysis of the debris at the testing site of the first United States' first thermonuclear weapon, Ivy Mike, (1 November 1952, Enewetak Atoll), revealed high concentrations of various actinides, including berkelium. For reasons of military secrecy, this result was not published until 1956.
Nuclear reactors produce mostly, among the berkelium isotopes, berkelium-249. During the storage and before the fuel disposal, most of it beta decays to californium-249. The latter has a half-life of 351 years, which is relatively long compared to the half-lives of other isotopes produced in the reactor, and is therefore undesirable in the disposal products.
The transuranium elements from americium to fermium, including berkelium, occurred naturally in the natural nuclear fission reactor at Oklo, but no longer do so.
Berkelium is also one of the elements that have theoretically been detected in Przybylski's Star.
History
Although very small amounts of berkelium were possibly produced in previous nuclear experiments, it was first intentionally synthesized, isolated and identified in December 1949 by Glenn T. Seaborg, Albert Ghiorso, Stanley Gerald Thompson, and Kenneth Street Jr. They used the 60-inch cyclotron at the University of California, Berkeley. Similar to the nearly simultaneous discovery of americium (element 95) and curium (element 96) in 1944, the new elements berkelium and californium (element 98) were both produced in 1949–1950. | Berkelium | Wikipedia | 387 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
The name choice for element 97 followed the previous tradition of the Californian group to draw an analogy between the newly discovered actinide and the lanthanide element positioned above it in the periodic table. Previously, americium was named after a continent as its analogue europium, and curium honored scientists Marie and Pierre Curie as the lanthanide above it, gadolinium, was named after the explorer of the rare-earth elements Johan Gadolin. Thus the discovery report by the Berkeley group reads: "It is suggested that element 97 be given the name berkelium (symbol Bk) after the city of Berkeley in a manner similar to that used in naming its chemical homologue terbium (atomic number 65) whose name was derived from the town of Ytterby, Sweden, where the rare earth minerals were first found." This tradition ended with berkelium, though, as the naming of the next discovered actinide, californium, was not related to its lanthanide analogue dysprosium, but after the discovery place.
The most difficult steps in the synthesis of berkelium were its separation from the final products and the production of sufficient quantities of americium for the target material. First, americium (241Am) nitrate solution was coated on a platinum foil, the solution was evaporated and the residue converted by annealing to americium dioxide (). This target was irradiated with 35 MeV alpha particles for 6 hours in the 60-inch cyclotron at the Lawrence Radiation Laboratory, University of California, Berkeley. The (α,2n) reaction induced by the irradiation yielded the 243Bk isotope and two free neutrons:
+ → + 2 | Berkelium | Wikipedia | 359 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
After the irradiation, the coating was dissolved with nitric acid and then precipitated as the hydroxide using concentrated aqueous ammonia solution. The product was centrifugated and re-dissolved in nitric acid. To separate berkelium from the unreacted americium, this solution was added to a mixture of ammonium and ammonium sulfate and heated to convert all the dissolved americium into the oxidation state +6. Unoxidized residual americium was precipitated by the addition of hydrofluoric acid as americium(III) fluoride (). This step yielded a mixture of the accompanying product curium and the expected element 97 in form of trifluorides. The mixture was converted to the corresponding hydroxides by treating it with potassium hydroxide, and after centrifugation, was dissolved in perchloric acid.
Further separation was carried out in the presence of a citric acid/ammonium buffer solution in a weakly acidic medium (pH≈3.5), using ion exchange at elevated temperature. The chromatographic separation behavior was unknown for the element 97 at the time, but was anticipated by analogy with terbium. The first results were disappointing because no alpha-particle emission signature could be detected from the elution product. With further analysis, searching for characteristic X-rays and conversion electron signals, a berkelium isotope was eventually detected. Its mass number was uncertain between 243 and 244 in the initial report, but was later established as 243.
Synthesis and extraction
Preparation of isotopes
Berkelium is produced by bombarding lighter actinides uranium (238U) or plutonium (239Pu) with neutrons in a nuclear reactor. In a more common case of uranium fuel, plutonium is produced first by neutron capture (the so-called (n,γ) reaction or neutron fusion) followed by beta-decay:
^{238}_{92}U ->[\ce{(n,\gamma)}] ^{239}_{92}U ->[\beta^-][23.5 \ \ce{min}] ^{239}_{93}Np ->[\beta^-][2.3565 \ \ce{d}] ^{239}_{94}Pu (the times are half-lives) | Berkelium | Wikipedia | 491 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
Plutonium-239 is further irradiated by a source that has a high neutron flux, several times higher than a conventional nuclear reactor, such as the 85-megawatt High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory in Tennessee, US. The higher flux promotes fusion reactions involving not one but several neutrons, converting 239Pu to 244Cm and then to 249Cm:
Curium-249 has a short half-life of 64 minutes, and thus its further conversion to 250Cm has a low probability. Instead, it transforms by beta-decay into 249Bk:
^{249}_{96}Cm ->[{\beta^-}][64.15 \ \ce{min}] ^{249}_{97}Bk ->[\beta^-][330 \ \ce{d}] ^{249}_{98}Cf
The thus-produced 249Bk has a long half-life of 330 days and thus can capture another neutron. However, the product, 250Bk, again has a relatively short half-life of 3.212 hours and thus does not yield any heavier berkelium isotopes. It instead decays to the californium isotope 250Cf:
^{249}_{97}Bk ->[\ce{(n,\gamma)}] ^{250}_{97}Bk ->[\beta^-][3.212 \ \ce{h}] ^{250}_{98}Cf
Although 247Bk is the most stable isotope of berkelium, its production in nuclear reactors is very difficult because its potential progenitor 247Cm has never been observed to undergo beta decay. Thus, 249Bk is the most accessible isotope of berkelium, which still is available only in small quantities (only 0.66 grams have been produced in the US over the period 1967–1983) at a high price of the order 185 USD per microgram. It is the only berkelium isotope available in bulk quantities, and thus the only berkelium isotope whose properties can be extensively studied. | Berkelium | Wikipedia | 442 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
The isotope 248Bk was first obtained in 1956 by bombarding a mixture of curium isotopes with 25 MeV α-particles. Although its direct detection was hindered by strong signal interference with 245Bk, the existence of a new isotope was proven by the growth of the decay product 248Cf which had been previously characterized. The half-life of 248Bk was estimated as hours, though later 1965 work gave a half-life in excess of 300 years (which may be due to an isomeric state). Berkelium-247 was produced during the same year by irradiating 244Cm with alpha-particles:
Berkelium-242 was synthesized in 1979 by bombarding 235U with 11B, 238U with 10B, 232Th with 14N or 232Th with 15N. It converts by electron capture to 242Cm with a half-life of minutes. A search for an initially suspected isotope 241Bk was then unsuccessful; 241Bk has since been synthesized.
Separation
The fact that berkelium readily assumes oxidation state +4 in solids, and is relatively stable in this state in liquids greatly assists separation of berkelium away from many other actinides. These are inevitably produced in relatively large amounts during the nuclear synthesis and often favor the +3 state. This fact was not yet known in the initial experiments, which used a more complex separation procedure. Various inorganic oxidation agents can be applied to the solutions to convert it to the +4 state, such as bromates (), bismuthates (), chromates ( and ), silver(I) thiolate (), lead(IV) oxide (), ozone (), or photochemical oxidation procedures. More recently, it has been discovered that some organic and bio-inspired molecules, such as the chelator called 3,4,3-LI(1,2-HOPO), can also oxidize Bk(III) and stabilize Bk(IV) under mild conditions. is then extracted with ion exchange, extraction chromatography or liquid-liquid extraction using HDEHP (bis-(2-ethylhexyl) phosphoric acid), amines, tributyl phosphate or various other reagents. These procedures separate berkelium from most trivalent actinides and lanthanides, except for the lanthanide cerium (lanthanides are absent in the irradiation target but are created in various nuclear fission decay chains). | Berkelium | Wikipedia | 512 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
A more detailed procedure adopted at the Oak Ridge National Laboratory was as follows: the initial mixture of actinides is processed with ion exchange using lithium chloride reagent, then precipitated as hydroxides, filtered and dissolved in nitric acid. It is then treated with high-pressure elution from cation exchange resins, and the berkelium phase is oxidized and extracted using one of the procedures described above. Reduction of the thus-obtained to the +3 oxidation state yields a solution, which is nearly free from other actinides (but contains cerium). Berkelium and cerium are then separated with another round of ion-exchange treatment.
Bulk metal preparation
In order to characterize chemical and physical properties of solid berkelium and its compounds, a program was initiated in 1952 at the Material Testing Reactor, Arco, Idaho, US. It resulted in preparation of an eight-gram plutonium-239 target and in the first production of macroscopic quantities (0.6 micrograms) of berkelium by Burris B. Cunningham and Stanley Gerald Thompson in 1958, after a continuous reactor irradiation of this target for six years. This irradiation method was and still is the only way of producing weighable amounts of the element, and most solid-state studies of berkelium have been conducted on microgram or submicrogram-sized samples.
The world's major irradiation sources are the 85-megawatt High Flux Isotope Reactor at the Oak Ridge National Laboratory in Tennessee, USA, and the SM-2 loop reactor at the Research Institute of Atomic Reactors (NIIAR) in Dimitrovgrad, Russia, which are both dedicated to the production of transcurium elements (atomic number greater than 96). These facilities have similar power and flux levels, and are expected to have comparable production capacities for transcurium elements, although the quantities produced at NIIAR are not publicly reported. In a "typical processing campaign" at Oak Ridge, tens of grams of curium are irradiated to produce decigram quantities of californium, milligram quantities of berkelium-249 and einsteinium, and picogram quantities of fermium. In total, just over one gram of berkelium-249 has been produced at Oak Ridge since 1967. | Berkelium | Wikipedia | 480 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
The first berkelium metal sample weighing 1.7 micrograms was prepared in 1971 by the reduction of fluoride with lithium vapor at 1000 °C; the fluoride was suspended on a tungsten wire above a tantalum crucible containing molten lithium. Later, metal samples weighing up to 0.5 milligrams were obtained with this method.
Similar results are obtained with fluoride. Berkelium metal can also be produced by the reduction of oxide with thorium or lanthanum.
Compounds
Oxides
Two oxides of berkelium are known, with the berkelium oxidation state of +3 () and +4 (). oxide is a brown solid, while oxide is a yellow-green solid with a melting point of 1920 °C and is formed from BkO2 by reduction with molecular hydrogen:
Upon heating to 1200 °C, the oxide undergoes a phase change; it undergoes another phase change at 1750 °C. Such three-phase behavior is typical for the actinide sesquioxides. oxide, BkO, has been reported as a brittle gray solid but its exact chemical composition remains uncertain.
Halides
In halides, berkelium assumes the oxidation states +3 and +4. The +3 state is the most stable, especially in solutions, while the tetravalent halides and are only known in the solid phase. The coordination of berkelium atom in its trivalent fluoride and chloride is tricapped trigonal prismatic, with the coordination number of 9. In trivalent bromide, it is bicapped trigonal prismatic (coordination 8) or octahedral (coordination 6), and in the iodide it is octahedral.
fluoride () is a yellow-green ionic solid and is isotypic with uranium tetrafluoride or zirconium tetrafluoride. fluoride () is also a yellow-green solid, but it has two crystalline structures. The most stable phase at low temperatures is isotypic with yttrium(III) fluoride, while upon heating to between 350 and 600 °C, it transforms to the structure found in lanthanum trifluoride. | Berkelium | Wikipedia | 452 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
Visible amounts of chloride () were first isolated and characterized in 1962, and weighed only 3 billionths of a gram. It can be prepared by introducing hydrogen chloride vapors into an evacuated quartz tube containing berkelium oxide at a temperature about 500 °C. This green solid has a melting point of 600 °C, and is isotypic with uranium(III) chloride. Upon heating to nearly melting point, converts into an orthorhombic phase.
Two forms of bromide are known: one with berkelium having coordination 6, and one with coordination 8. The latter is less stable and transforms to the former phase upon heating to about 350 °C. An important phenomenon for radioactive solids has been studied on these two crystal forms: the structure of fresh and aged 249BkBr3 samples was probed by X-ray diffraction over a period longer than 3 years, so that various fractions of berkelium-249 had beta decayed to californium-249. No change in structure was observed upon the 249BkBr3—249CfBr3 transformation. However, other differences were noted for 249BkBr3 and 249CfBr3. For example, the latter could be reduced with hydrogen to 249CfBr2, but the former could not – this result was reproduced on individual 249BkBr3 and 249CfBr3 samples, as well on the samples containing both bromides. The intergrowth of californium in berkelium occurs at a rate of 0.22% per day and is an intrinsic obstacle in studying berkelium properties. Beside a chemical contamination, 249Cf, being an alpha emitter, brings undesirable self-damage of the crystal lattice and the resulting self-heating. The chemical effect however can be avoided by performing measurements as a function of time and extrapolating the obtained results.
Other inorganic compounds
The pnictides of berkelium-249 of the type BkX are known for the elements nitrogen, phosphorus, arsenic and antimony. They crystallize in the rock-salt structure and are prepared by the reaction of either hydride () or metallic berkelium with these elements at elevated temperature (about 600 °C) under high vacuum.
sulfide, , is prepared by either treating berkelium oxide with a mixture of hydrogen sulfide and carbon disulfide vapors at 1130 °C, or by directly reacting metallic berkelium with elemental sulfur. These procedures yield brownish-black crystals. | Berkelium | Wikipedia | 511 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
and hydroxides are both stable in 1 molar solutions of sodium hydroxide. phosphate () has been prepared as a solid, which shows strong fluorescence under excitation with a green light. Berkelium hydrides are produced by reacting metal with hydrogen gas at temperatures about 250 °C. They are non-stoichiometric with the nominal formula (0 < x < 1). Several other salts of berkelium are known, including an oxysulfide (), and hydrated nitrate (), chloride (), sulfate () and oxalate (). Thermal decomposition at about 600 °C in an argon atmosphere (to avoid oxidation to ) of yields the crystals of oxysulfate (). This compound is thermally stable to at least 1000 °C in inert atmosphere.
Organoberkelium compounds
Berkelium forms a trigonal (η5–C5H5)3Bk metallocene complex with three cyclopentadienyl rings, which can be synthesized by reacting chloride with the molten beryllocene () at about 70 °C. It has an amber color and a density of 2.47 g/cm3. The complex is stable to heating to at least 250 °C, and sublimates without melting at about 350 °C. The high radioactivity of berkelium gradually destroys the compound (within a period of weeks). One cyclopentadienyl ring in (η5–C5H5)3Bk can be substituted by chlorine to yield . The optical absorption spectra of this compound are very similar to those of (η5–C5H5)3Bk.
Applications
There is currently no use for any isotope of berkelium outside basic scientific research. Berkelium-249 is a common target nuclide to prepare still heavier transuranium elements and superheavy elements, such as lawrencium, rutherfordium and bohrium. It is also useful as a source of the isotope californium-249, which is used for studies on the chemistry of californium in preference to the more radioactive californium-252 that is produced in neutron bombardment facilities such as the HFIR. | Berkelium | Wikipedia | 458 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
A 22 milligram batch of berkelium-249 was prepared in a 250-day irradiation and then purified for 90 days at Oak Ridge in 2009. This target yielded the first 6 atoms of tennessine at the Joint Institute for Nuclear Research (JINR), Dubna, Russia, after bombarding it with calcium ions in the U400 cyclotron for 150 days. This synthesis was a culmination of the Russia-US collaboration between JINR and Lawrence Livermore National Laboratory on the synthesis of elements 113 to 118 which was initiated in 1989.
Nuclear fuel cycle
The nuclear fission properties of berkelium are different from those of the neighboring actinides curium and californium, and they suggest berkelium to perform poorly as a fuel in a nuclear reactor. Specifically, berkelium-249 has a moderately large neutron capture cross section of 710 barns for thermal neutrons, 1200 barns resonance integral, but very low fission cross section for thermal neutrons. In a thermal reactor, much of it will therefore be converted to berkelium-250 which quickly decays to californium-250. In principle, berkelium-249 can sustain a nuclear chain reaction in a fast breeder reactor. Its critical mass is relatively high at 192 kg, which can be reduced with a water or steel reflector but would still exceed the world production of this isotope.
Berkelium-247 can maintain a chain reaction both in a thermal-neutron and in a fast-neutron reactor, however, its production is rather complex and thus the availability is much lower than its critical mass, which is about 75.7 kg for a bare sphere, 41.2 kg with a water reflector and 35.2 kg with a steel reflector (30 cm thickness). | Berkelium | Wikipedia | 366 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
Health issues
Little is known about the effects of berkelium on human body, and analogies with other elements may not be drawn because of different radiation products (electrons for berkelium and alpha particles, neutrons, or both for most other actinides). The low energy of electrons emitted from berkelium-249 (less than 126 keV) hinders its detection, due to signal interference with other decay processes, but also makes this isotope relatively harmless to humans as compared to other actinides. However, berkelium-249 transforms with a half-life of only 330 days to the strong alpha-emitter californium-249, which is rather dangerous and has to be handled in a glovebox in a dedicated laboratory.
Most available berkelium toxicity data originate from research on animals. Upon ingestion by rats, only about 0.01% of berkelium ends in the blood stream. From there, about 65% goes to the bones, where it remains for about 50 years, 25% to the lungs (biological half-life about 20 years), 0.035% to the testicles or 0.01% to the ovaries where berkelium stays indefinitely. The balance of about 10% is excreted. In all these organs berkelium might promote cancer, and in the skeleton, its radiation can damage red blood cells. The maximum permissible amount of berkelium-249 in the human skeleton is 0.4 nanograms. | Berkelium | Wikipedia | 307 | 3758 | https://en.wikipedia.org/wiki/Berkelium | Physical sciences | Chemical elements_2 | null |
Bauxite () is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (), boehmite (γ-AlO(OH)) and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite (FeO(OH)) and haematite (), the aluminium clay mineral kaolinite () and small amounts of anatase () and ilmenite ( or ).
Bauxite appears dull in luster and is reddish-brown, white, or tan.
In 1821, the French geologist Pierre Berthier discovered bauxite near the village of Les Baux in Provence, southern France.
Formation
Numerous classification schemes have been proposed for bauxite but, , there was no consensus.
Vadász (1951) distinguished lateritic bauxites (silicate bauxites) from karst bauxite ores (carbonate bauxites):
The carbonate bauxites occur predominantly in Europe, Guyana, Suriname, and Jamaica above carbonate rocks (limestone and dolomite), where they were formed by lateritic weathering and residual accumulation of intercalated clay layers – dispersed clays which were concentrated as the enclosing limestones gradually dissolved during chemical weathering.
The lateritic bauxites are found mostly in the countries of the tropics. They were formed by lateritization of various silicate rocks such as granite, gneiss, basalt, syenite, and shale. In comparison with the iron-rich laterites, the formation of bauxites depends even more on intense weathering conditions in a location with very good drainage. This enables the dissolution of the kaolinite and the precipitation of the gibbsite. Zones with highest aluminium content are frequently located below a ferruginous surface layer. The aluminium hydroxide in the lateritic bauxite deposits is almost exclusively gibbsite.
In the case of Jamaica, recent analysis of the soils showed elevated levels of cadmium, suggesting that the bauxite originates from Miocene volcanic ash deposits from episodes of significant volcanism in Central America.
Production and reserves | Bauxite | Wikipedia | 461 | 3760 | https://en.wikipedia.org/wiki/Bauxite | Physical sciences | Petrology | null |
Australia is the largest producer of bauxite, followed by Guinea and China. Bauxite is usually strip mined because it is almost always found near the surface of the terrain, with little or no overburden. Increased aluminium recycling, which requires less electric power than producing aluminium from ores, may considerably extend the world's bauxite reserves.
Aluminium production
, approximately 70% to 80% of the world's dry bauxite production is processed first into alumina and then into aluminium by electrolysis. Bauxite rocks are typically classified according to their intended commercial application: metallurgical, abrasive, cement, chemical, and refractory.
Bauxite ore is usually heated in a pressure vessel along with a sodium hydroxide solution at a temperature of . At these temperatures, the aluminium is dissolved as sodium aluminate (the Bayer process). The aluminium compounds in the bauxite may be present as gibbsite (Al(OH)3), boehmite (AlOOH) or diaspore (AlOOH); the different forms of the aluminium component will dictate the extraction conditions. The undissolved waste, bauxite tailings, after the aluminium compounds are extracted contains iron oxides, silica, calcia, titania and some un-reacted alumina. After separation of the residue by filtering, pure gibbsite is precipitated when the liquid is cooled, and then seeded with fine-grained aluminium hydroxide. The gibbsite is usually converted into aluminium oxide, Al2O3, by heating in rotary kilns or fluid flash calciners to a temperature in excess of . This aluminium oxide is dissolved at a temperature of about in molten cryolite. Next, this molten substance can yield metallic aluminium by passing an electric current through it in the process of electrolysis, which is called the Hall–Héroult process, named after its American and French discoverers.
Prior to the invention of this process, and prior to the Deville process, aluminium ore was refined by heating ore along with elemental sodium or potassium in a vacuum. The method was complicated and consumed materials that were themselves expensive at that time. This made early elemental aluminium more expensive than gold. | Bauxite | Wikipedia | 460 | 3760 | https://en.wikipedia.org/wiki/Bauxite | Physical sciences | Petrology | null |
Maritime safety
As a bulk cargo, bauxite is a Group A cargo that may liquefy if excessively moist. Liquefaction and the free surface effect can cause the cargo to shift rapidly inside the hold and make the ship unstable, potentially sinking the ship. One vessel suspected to have been sunk in this way was the MS Bulk Jupiter in 2015. One method which can demonstrate this effect is the "can test", in which a sample of the material is placed in a cylindrical can and struck against a surface many times. If a moist slurry forms in the can, then there is a likelihood for the cargo to liquefy; although conversely, even if the sample remains dry it does not conclusively prove that it will remain that way, or that it is safe for loading.
Source of gallium
Bauxite is the main source of the rare metal gallium.
During the processing of bauxite to alumina in the Bayer process, gallium accumulates in the sodium hydroxide liquor. From this it can be extracted by a variety of methods. The most recent is the use of ion-exchange resin. Achievable extraction efficiencies critically depend on the original concentration in the feed bauxite. At a typical feed concentration of 50 ppm, about 15 percent of the contained gallium is extractable. The remainder reports to the red mud and aluminium hydroxide streams.
Bauxite is also a potential source for vanadium.
Socio-ecological impacts
The social and environmental impacts of bauxite extraction are well documented. Most of the world's bauxite deposits can be found within of the earths surface. Strip mining is the most common technique used for extracting shallow bauxite. This process involves removing the vegetation, top soil, and overburden to expose the bauxite ore. The overlying soil is typically stockpiled in order to rehabilitate the mine once operations have finished. During the strip mining process, the biodiversity and habitat once present in the area is completely lost and the hydrological and soil characteristics in the region are permanently altered. Other environmental impacts of bauxite mining include soil degradation, air pollution, and water pollution.
Red mud | Bauxite | Wikipedia | 453 | 3760 | https://en.wikipedia.org/wiki/Bauxite | Physical sciences | Petrology | null |
Red mud is a highly alkaline sludge, with a high pH around 13, that is a byproduct of the Bayer process. It contains several elements such as sodium aluminoscilicate, calcium titanate, monohydrate aluminium, and trihydrate aluminium that do not break down in nature. When improperly stored, red mud can contaminate soil and water, which can result in local extinction of all life. Red mud was responsible for killing all life in the Marcal River in Hungary after a spill occurred in 2010. When red mud dries, it turns into dust that can cause lung disease, cancer and birth defects.
Conflicts
In the tropical regions of Asia, central Africa, South America and northern Australia, there has been an increase of bauxite mines on traditional and indigenous lands. This has resulted in a number of negative social impacts on local and indigenous peoples. In the Boké Region of Guinea, there has been a significant increase in bauxite mining pressure on the local population. This has resulted in potable water issues, air pollution, food contamination, and land expropriation disputes due to improper compensation.
Bauxite mining has led to protests, civil unrest, and violent conflicts in Guinea, Ghana, Vietnam, and India.
Guinea
Guinea has a long history of mining related conflicts between communities and mining companies. Between 2015 and 2018, new bauxite mining operations in the Boké Region of Guinea have caused in 35 conflicts which include movements of revolts and road blockades. These conflicts have resulted in the loss of human life, the destruction of heavy machinery, and damage to government buildings. | Bauxite | Wikipedia | 335 | 3760 | https://en.wikipedia.org/wiki/Bauxite | Physical sciences | Petrology | null |
Ghana
The Atewa range in Ghana, classified as an ecologically important forest reserve with an area of , has been is a recent site of conflict and controversy surrounding baxuite mining. The forest reserve is one of the only two upland evergreen forests in Ghana, and makes up a significant portion of the remaining 20% of forested habitat left in Ghana. The Atewa range falls under the jurisdiction of Akyem Abuakwa Traditional Area and is overseen by the king known as Okyenhene. In 2013, an NGO called A Rocha Ghana held a summit with the forestry and water resource commission, the minister of lands, the minister of the environment, and other important stakeholders. They came to the conclusion that no future government should mine bauxite in the region because the reserve is environmentally and culturally significant. In 2016, the government along with NGO's began the process of upgrading the reserved to a national park. However, that year an election took place, and before it became official, the newly elected National Patriotic Party (NPP) rejected the plan. In 2017, the government of Ghana signed a Memorandum of Understanding with China to develop new bauxite mining infrastructure in Ghana. Although there was no official plan to mine the Atewa Forest Reserve, tensions between local communities, NGO and the government began to rise. In 2019, tensions began to reach a peak when the government presented the Ghana Integrated Bauxite and Aluminium Development Authority Act that would create the legal framework required to develop and establish an integrated bauxite industry. In may of that year, the government began drilling deep holes in the reserve. These actions sparked several protests, including a march from the reserve to the presidential palace, an informational billboard campaign led by A Rocha Ghana, and a youth march. In 2020, A Rocha Ghana also sued the government over the drilling in the reserve after they failed to provide a statement explaining their actions. | Bauxite | Wikipedia | 387 | 3760 | https://en.wikipedia.org/wiki/Bauxite | Physical sciences | Petrology | null |
Vietnam
In early 2009, the Vietnamese Government proposed a plan to mine remote regions of the central highlands. This proposal was highly controversial and sparked a nationwide debate and the most significant domestic conflict since the Vietnam War. Government scientists, journalists, religious leaders, retired high level state officials, and General Võ Nguyên Giáp, the military leader of anti-colonial revolution, were among the many people across Vietnamese society who opposed the governments plans. In an attempt to stop the spread of information across the globe, the government banned domestic reporters from reporting on bauxite mining. However, reporters turned to Vietnamese language websites and blogs where the reporting and discussion continued. On April 12, 2009, several well-respected Vietnamese scholars started a petition against the mining of bauxite that was signed by 135 accomplished and well known "Intellectuals". This petition helped unite the scattered anti-bauxite movement into a unified opposition against the state. These acts of governmental defiance were met with repressive state actions. Many domestic online reporters were arrested, and legislative action was taken to repress scientific research.
India
Most of India's bauxite ore reserves, which are among the top ten largest in the world, are located on tribal land. These tribal lands are densely populated and home to over 100 million Indigenous Indian peoples. The mountain summits located on these lands act as a source of water and greatly contribute to the regions fertility. The Indian bauxite industry is interested in developing this land for aluminum production, which poses great risk to the terrestrial and aquatic ecosystems. Historically, the Indigenous peoples living on these lands have shown resistance to development, and oppose any new bauxite mining projects in the area. This has led to violent conflicts between Indigenous communities and police. On December 16, 2000, police killed three Indigenous protestors and wounded over a dozen more during a protest over a bauxite project in the Rayagada district of Odisha. | Bauxite | Wikipedia | 385 | 3760 | https://en.wikipedia.org/wiki/Bauxite | Physical sciences | Petrology | null |
A book is a medium for recording information in the form of writing or images. Modern books are typically in codex format, composed of many pages that are bound together and protected by a cover; they were preceded by several earlier formats, including the scroll and the tablet. The book publishing process is the series of steps involved in their creation and dissemination.
As a conceptual object, a book refers to a written work of substantial length, which may be distributed either physically or digitally as an ebook. These works can be broadly classified into fiction (containing invented content, often narratives) and non-fiction (containing content intended as factual truth). A physical book may not contain such a work: for example, it may contain only drawings, engravings, photographs, puzzles, or removable content like paper dolls. It may also be left empty for personal use, as in the case of account books, appointment books, autograph books, notebooks, diaries and sketchbooks.
Books are sold at both regular stores and specialized bookstores, as well as online for delivery, and can be borrowed from libraries. The reception of books has led to a number of social consequences, including censorship.
The modern book industry has seen several major changes due to new technologies, including ebooks and audiobooks (recordings of books being read aloud). Awareness of the needs of print-disabled people has led to a rise in formats designed for greater accessibility, such as braille printing and large-print editions. Google Books estimated in 2010 that approximately 130 million total unique books had been published.
Etymology
The word book comes from the Old English , which in turn likely comes from the Germanic root , cognate to "beech". In Slavic languages like Russian, Bulgarian, Macedonian —"letter" is cognate with "beech". In Russian, Serbian and Macedonian, the word () or () refers to a primary school textbook that helps young children master the techniques of reading and writing. It is thus conjectured that the earliest Indo-European writings may have been carved on beech wood. The Latin word , meaning a book in the modern sense (bound and with separate leaves), originally meant "block of wood".
An avid reader or collector of books is a bibliophile, or colloquially a "bookworm". | Book | Wikipedia | 462 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Definitions
In its modern incarnation, a book is typically composed of many pages (commonly of paper, parchment, or vellum) that are bound together along one edge and protected by a cover. By extension, book refers to a physical book's written, printed, or graphic contents. A single part or division of a longer written work may also be called a book, especially for some works composed in antiquity: each part of Aristotle's Physics, for example, is a book.
It is difficult to create a precise definition of the book that clearly delineates it from other kinds of written material across time and culture. The meaning of the term has changed substantially over time with the evolution of communication media. Historian of books James Raven has suggested that when studying how books have been used to communicate, they should be defined in a broadly inclusive way as "portable, durable, replicable and legible" means of recording and disseminating information, rather than relying on physical or contextual features. This would include, for example, ebooks, newspapers, and quipus (a form of knot-based recording historically used by cultures in Andean South America), but not objects fixed in place such as inscribed monuments.
A stricter definition is given by UNESCO: for the purpose of recording national statistics on book production, it recommended that a book be defined as "a non-periodical printed publication of at least 49 pages, exclusive of the cover pages, published in the country and made available to the public", distinguishing them from other written material such as pamphlets. Kovač et al. have critiqued this definition for failing to account for new digital formats. They propose four criteria (a minimum length; textual content; a form with defined boundaries; and "information architecture" like linear structure and certain textual elements) that form a "hierarchy of the book", in which formats that fulfill more criteria are considered more similar to the traditional printed book.
Although in academic language a monograph is a specialist work on a single subject, in library and information science the term is used more broadly to mean any non-serial publication complete in one volume (a physical book) or a definite number of volumes (such as a multi-volume novel), in contrast to serial or periodical publications.
History | Book | Wikipedia | 458 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
The history of books became an acknowledged academic discipline in the 1980s. Contributions to the field have come from textual scholarship, codicology, bibliography, philology, palaeography, art history, social history and cultural history. It aims to demonstrate that the book as an object, not just the text contained within it, is a conduit of interaction between readers and words. Analysis of each component part of the book can reveal its purpose, where and how it was kept, who read it, ideological and religious beliefs of the period, and whether readers interacted with the text within. Even a lack of such evidence can leave valuable clues about the nature of a particular book.
The earliest forms of writing were etched on tablets, transitioning to palm leaves and papyrus in ancient times. Parchment and paper later emerged as important substrates for bookmaking, introducing greater durability and accessibility. Across regions like China, the Middle East, Europe, and South Asia, diverse methods of book production evolved. The Middle Ages saw the rise of illuminated manuscripts, intricately blending text and imagery, particularly during the Mughal era in South Asia under the patronage of rulers like Akbar and Shah Jahan.
Prior to the invention of the printing press in the 15th century, made famous by the Gutenberg Bible, each text was a unique handcrafted valuable article, personalized through the design features incorporated by the scribe, owner, bookbinder, and illustrator. Its creation marked a pivotal moment for book production. Innovations like movable type and steam-powered presses accelerated manufacturing processes and contributed to increased literacy rates. Copyright protection also emerged, securing authors' rights and shaping the publishing landscape. The Late Modern Period introduced chapbooks, catering to a wider range of readers, and mechanization of the printing process further enhanced efficiency.
The 20th century witnessed the advent of typewriters, computers, and desktop publishing, transforming document creation and printing. Digital advancements in the 21st century led to the rise of ebooks, propelled by the popularity of ereaders and accessibility features. While discussions about the potential decline of physical books have surfaced, print media has proven remarkably resilient, continuing to thrive as a multi-billion dollar industry. Additionally, efforts to make literature more inclusive emerged, with the development of Braille for the visually impaired and the creation of spoken books, providing alternative ways for individuals to access and enjoy literature. | Book | Wikipedia | 481 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Tablet
Some of the earliest written records were made on tablets. Clay tablets (flattened pieces of clay impressed with a stylus) were used in the Ancient Near East throughout the Bronze Age and well into the Iron Age, especially for writing in cuneiform. Wax tablets (pieces of wood covered in a layer of wax) were used in classical antiquity and throughout the Middle Ages.
The custom of binding several wax tablets together (Roman pugillares) is a possible precursor of modern bound books. The etymology of the word codex (block of wood) suggests that it may have developed from wooden wax tablets.
Scroll
Scrolls made from papyrus were first used for writing in Ancient Egypt, perhaps as early as the First Dynasty, although the earliest evidence is from the account books of King Neferirkare Kakai of the Fifth Dynasty (about 2400 BC). According to Herodotus (History 5:58), the Phoenicians brought writing and papyrus to Greece around the 10th or 9th century BC. Whether made from papyrus, parchment, or paper, scrolls were the dominant writing medium in the Hellenistic, Roman, Chinese, Hebrew, and Macedonian cultures. The codex dominated in the Roman world by late antiquity, but scrolls persisted much longer in Asia.
Codex
The codex is the ancestor of the modern book, consisting of sheets of uniform size bound along one edge and typically held between two covers made of some more robust material. Isidore of Seville (died 636) explained the then-current relation between a codex, book, and scroll in his Etymologiae (VI.13): "A codex is composed of many books; a book is of one scroll. It is called codex by way of metaphor from the trunks (codex) of trees or vines, as if it were a wooden stock, because it contains in itself a multitude of books, as it were of branches". | Book | Wikipedia | 382 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
The first written mention of the codex as a form of book is from Martial, in his Apophoreta CLXXXIV at the end of the first century, where he praises its compactness. However, the codex never gained much popularity in the pagan Hellenistic world, and only within the Christian community did it gain widespread use. This change happened gradually during the 3rd and 4th centuries, and the reasons for adopting the codex form of the book were several: the format was more economical than the scroll, as both sides of the writing material can be used; and it was portable, searchable, and easier to conceal. The Christian authors may also have wanted to distinguish their writings from the pagan and Judaic texts written on scrolls.
The codices of pre-Columbian Mesoamerica had the same form as the European codex, but were instead made with long folded strips of either fig bark (amatl) or plant fibers, often with a layer of whitewash applied before writing. New World codices were written as late as the 16th century (see Maya codices and Aztec codices). Those written before the Spanish conquests seem all to have been single long sheets folded concertina-style, sometimes written on both sides of the local amatl paper.
Manuscript
Manuscripts, handwritten and hand-copied documents, were the only form of writing before the invention and widespread adoption of print. Advances were made in the techniques used to create them.
In the early Western Roman Empire, monasteries continued Latin writing traditions related to Christianity, and the clergy were the predominant readers and copyists. The bookmaking process was long and laborious. They were usually written on parchment or vellum, writing surfaces made from processed animal skin. The parchment had to be prepared, then the unbound pages were planned and ruled with a blunt tool or lead, after which the text was written by a scribe, who usually left blank areas for illustration and rubrication. Finally, it was bound by a bookbinder.
Because of the difficulties involved in making and copying books, they were expensive and rare. Smaller monasteries usually had only a few dozen books. By the 9th century, larger collections held around 500 volumes and even at the end of the Middle Ages, the papal library in Avignon and Paris library of the Sorbonne held only around 2,000 volumes. | Book | Wikipedia | 471 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
The rise of universities in the 13th century led to an increased demand for books, and a new system for copying appeared. The books were divided into unbound leaves (pecia), which were lent out to different copyists, so the speed of book production was considerably increased. The system was maintained by secular stationers guilds, which produced both religious and non-religious material.In India, bound manuscripts made of birch bark or palm leaf had existed since antiquity. The text in palm leaf manuscripts was inscribed with a knife pen on rectangular cut and cured palm leaf sheets; coloring was then applied to the surface and wiped off, leaving the ink in the incised grooves. Each sheet typically had a hole through which a string could pass, and with these the sheets were tied together with a string to bind like a book.
Woodblock printing
In woodblock printing, a relief image of an entire page is carved into blocks of wood, inked, and used to print copies of that page. It originated in the Han dynasty before 220 AD, used to print textiles and later paper, and was widely used throughout East Asia. The oldest dated book printed by this method is The Diamond Sutra (868 AD). The method (called woodcut when used in art) arrived in Europe in the early 14th century. Books (known as block-books), as well as playing-cards and religious pictures, began to be produced by this method. Creating an entire book was a painstaking process, requiring a hand-carved block for each page, and the wooden blocks could crack if stored for too long.
Movable type and incunabula
The Chinese inventor Bi Sheng made movable type of earthenware , but there are no known surviving examples of his printing. Around 1450, Johannes Gutenberg independently invented movable type in Europe, along with innovations in casting the type based on a matrix and hand mould. This invention gradually made books less expensive to produce and more widely available. Early printed books, single sheets and images which were created before 1501 in Europe are known as incunables or incunabula. | Book | Wikipedia | 426 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
19th century to present
Steam-powered printing presses became popular in the early 19th century. These machines could print 1,100 sheets per hour, but workers could only set 2,000 letters per hour. Monotype and linotype typesetting machines were introduced in the late 19th century. They could set more than 6,000 letters per hour and an entire line of type at once. There have been numerous improvements in the printing press. In mid-20th century, European book production had risen to over 200,000 titles per year.
During the 20th century, libraries faced an ever-increasing rate of publishing, sometimes called an information explosion. The advent of electronic publishing and the internet means that new information is often published online rather than in printed books, for example through a digital library. "Print on demand" technologies, which make it possible to print as few as one book at a time, have made self-publishing (and vanity publishing) much easier and more affordable, and has allowed publishers to keep low-selling books in print rather than declaring them out of print.
Contemporary publishing
Presently, books are typically produced by a publishing company in order to be put on the market by distributors and bookstores. The publisher negotiates a formal legal agreement with authors in order to obtain the copyright to works, then arranges for them to be produced and sold. The major steps of the publishing process are: editing and proofreading the work to be published; designing the printed book; manufacturing the books; and selling the books, including marketing and promotion. Each of these steps is usually taken on by third-party companies paid by the publisher. This is in contrast to self-publishing, where an author pays for the production and distribution of their own work and manages some or all steps of the publishing process.
English-language publishing is currently dominated by the so-called "Big Five" publishers: Penguin Random House, Hachette Book Group, HarperCollins, Simon & Schuster, and Macmillan Publishers. They were estimated to make up almost 60 percent of the market for general-readership books in 2021.
Design
Book design is the art of incorporating the content, style, format, design, and sequence of the various elements of a book into a coherent unit.
Layout | Book | Wikipedia | 454 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Modern books are organized according to a particular format called the book's layout. Although there is great variation in layout, modern books tend to adhere to a set of rules with regard to what the parts of the layout are and what their content usually includes. A basic layout will include a front cover, a back cover and the book's content which is called its body copy or content pages. The front cover often bears the book's title (and subtitle, if any) and the name of its author or editor(s). The inside front cover page is usually left blank in both hardcover and paperback books. The next section, if present, is the book's front matter, which includes all textual material after the front cover but not part of the book's content such as a foreword, a dedication, a table of contents and publisher data such as the book's edition or printing number and place of publication. Between the body copy and the back cover goes the end matter which would include any indices, sets of tables, diagrams, glossaries or lists of cited works (though an edited book with several authors usually places cited works at the end of each authored chapter). The inside back cover page, like that inside the front cover, is usually blank. The back cover is the usual place for the book's ISBN and maybe a photograph of the author(s)/ editor(s), perhaps with a short introduction to them. Also here often appear plot summaries, barcodes and excerpted reviews of the book.
The body of the books is usually divided into parts, chapters, sections and sometimes subsections that are composed of at least a paragraph or more.
Size | Book | Wikipedia | 345 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
The size of a book is generally measured by the height against the width of a leaf, or sometimes the height and width of its cover. A series of terms commonly used by contemporary libraries and publishers for the general sizes of modern books ranges from folio (the largest), to quarto (smaller) and octavo (still smaller). Historically, these terms referred to the format of the book, a technical term used by printers and bibliographers to indicate the size of a leaf in terms of the size of the original sheet. For example, a quarto was a book printed on sheets of paper folded in half twice, with the first fold at right angles to the second, to produce 4 leaves (or 8 pages), each leaf one fourth the size of the original sheet printed – note that a leaf refers to the single piece of paper, whereas a page is one side of a leaf. Because the actual format of many modern books cannot be determined from examination of the books, bibliographers may not use these terms in scholarly descriptions.
Illustration
While some form of book illustration has existed since the invention of writing, the modern Western tradition of illustration began with 15th-century block books, in which the book's text and images were cut into the same block. Techniques such as engraving, etching, and lithography have also been influential.
Manufacturing
The methods used for the printing and binding of books continued fundamentally unchanged from the 15th century into the early 20th century. While there was more mechanization, a book printer in 1900 still used movable metal type assembled into words, lines, and pages to create copies. Modern paper books are printed on paper designed specifically for printing. Traditionally, book papers are off-white or low-white papers (easier to read), are opaque to minimize the show-through of text from one side of the page to the other and are (usually) made to tighter caliper or thickness specifications, particularly for case-bound books. Different paper qualities are used depending on the type of book: Machine finished coated papers, woodfree uncoated papers, coated fine papers and special fine papers are common paper grades. | Book | Wikipedia | 443 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Today, the majority of books are printed by offset lithography. When a book is printed, the pages are laid out on the plate so that after the printed sheet is folded the pages will be in the correct sequence. Books tend to be manufactured nowadays in a few standard sizes. The sizes of books are usually specified as "trim size": the size of the page after the sheet has been folded and trimmed. The standard sizes result from sheet sizes (therefore machine sizes) which became popular 200 or 300 years ago, and have come to dominate the industry. British conventions in this regard prevail throughout the English-speaking world, except for the US. The European book manufacturing industry works to a completely different set of standards.
Hardcover books have a stiff binding, while paperback books have cheaper, flexible covers which tend to be less durable. Publishers may produce low-cost pre-publication copies known as galleys or "bound proofs" for promotional purposes, such as generating reviews in advance of publication. Galleys are usually made as cheaply as possible, since they are not intended for sale.
Printing
Some books, particularly those with shorter runs (i.e. with fewer copies) will be printed on sheet-fed offset presses, but most books are now printed on web presses, which are fed by a continuous roll of paper, and can consequently print more copies in a shorter time. As the production line circulates, a complete "book" is collected together in one stack of pages, and another machine carries out the folding, pleating, and stitching of the pages into bundles of signatures (sections of pages) ready to go into the gathering line. The pages of a book are printed two at a time, not as one complete book. Excess numbers are printed to make up for any spoilage due to make-readies or test pages to assure final print quality.
A make-ready is the preparatory work carried out by the pressmen to get the printing press up to the required quality of impression. Included in make-ready is the time taken to mount the plate onto the machine, clean up any mess from the previous job, and get the press up to speed. As soon as the pressman decides that the printing is correct, all the make-ready sheets will be discarded, and the press will start making books. Similar make readies take place in the folding and binding areas, each involving spoilage of paper. | Book | Wikipedia | 492 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Recent developments in book manufacturing include the development of digital printing. Book pages are printed, in much the same way as an office copier works, using toner rather than ink. Each book is printed in one pass, not as separate signatures. Digital printing has permitted the manufacture of much smaller quantities than offset, in part because of the absence of make readies and of spoilage. Digital printing has opened up the possibility of print-on-demand, where no books are printed until after an order is received from a customer.
Binding
After the signatures are folded and gathered, they move into the bindery. In the middle of last century there were still many trade binders—stand-alone binding companies which did no printing, specializing in binding alone. At that time, because of the dominance of letterpress printing, typesetting and printing took place in one location, and binding in a different factory. When type was all metal, a typical book's worth of type would be bulky, fragile and heavy. The less it was moved in this condition the better: so printing would be carried out in the same location as the typesetting. Printed sheets on the other hand could easily be moved. Now, because of increasing computerization of preparing a book for the printer, the typesetting part of the job has flowed upstream, where it is done either by separately contracting companies working for the publisher, by the publishers themselves, or even by the authors. Mergers in the book manufacturing industry mean that it is now unusual to find a bindery which is not also involved in book printing (and vice versa).
If the book is a hardback its path through the bindery will involve more points of activity than if it is a paperback. Unsewn binding is now increasingly common. The signatures of a book can also be held together by "Smyth sewing" using needles, "McCain sewing", using drilled holes often used in schoolbook binding, or "notch binding", where gashes about an inch long are made at intervals through the fold in the spine of each signature. The rest of the binding process is similar in all instances. Sewn and notch bound books can be bound as either hardbacks or paperbacks. | Book | Wikipedia | 449 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Finishing
"Making cases" happens off-line and prior to the book's arrival at the binding line. In the most basic case-making, two pieces of cardboard are placed onto a glued piece of cloth with a space between them into which is glued a thinner board cut to the width of the spine of the book. The overlapping edges of the cloth (about 5/8" all round) are folded over the boards, and pressed down to adhere. After case-making the stack of cases will go to the foil stamping area for adding decorations and type.
Retail and distribution
Bookselling is the commercial trading of books that forms the retail and distribution end of the publishing process.
Accessible publishing
Accessible publishing is an approach to publishing and book design whereby books and other texts are made available in alternative formats designed to aid or replace the reading process. It is particularly relevant for people who are blind, visually impaired or otherwise print-disabled.
Alternative formats that have been developed to aid different people to read include varieties of larger fonts, specialized fonts for certain kinds of reading disabilities, braille, ebooks, and automated audiobooks and DAISY digital talking books.
Accessible publishing has been made easier through developments in technology such as print on demand, ebook readers, the XML structured data format, the EPUB3 format and the Internet.
Audiobooks
An audiobook or talking book is a recording of a book or other work being read out loud. A reading of the complete text is described as "unabridged", while readings of shorter versions are abridgements.
Spoken audio has been available in schools and public libraries and to a lesser extent in music shops since the 1930s. Many spoken word albums were made prior to the age of cassettes, compact discs, and downloadable audio, often of poetry and plays rather than books. It was not until the 1980s that the medium began to attract book retailers, and then book retailers started displaying audiobooks on bookshelves rather than in separate displays.
Ebooks
An ebook (short for electronic book), also spelled e-book or eBook, is a book publication made available in electronic form, consisting of text, images, or both, readable on the flat-panel display of computers or other electronic devices. Although sometimes defined as "an electronic version of a printed book", some ebooks exist without a printed equivalent. Ebooks can be read on dedicated e-reader devices and on any computer device that features a controllable viewing screen, including desktop computers, laptops, tablets and smartphones. | Book | Wikipedia | 511 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
In some markets, the sale of printed books has decreased due to the increased use of ebooks. However, printed books still largely outsell ebooks, and many people have a preference for print.
Dummy books
Dummy books (or faux books) are books that are designed to imitate a real book by appearance to deceive people, some books may be whole with empty pages, others may be hollow or in other cases, there may be a whole panel carved with spines which are then painted to look like books, titles of some books may also be fictitious.
There are many reasons to have dummy books on display such as; to allude visitors of the vast wealth of information in their possession and to inflate the owner's appearance of wealth, to conceal something, for shop displays or for decorative purposes.
In early 19th century at Gwrych Castle, North Wales, Lloyd Hesketh Bamford-Hesketh was known for his vast collection of books at his library, however, at the later part of that same century, the public became aware that parts of his library was a fabrication, dummy books were built and then locked behind glass doors to stop people from trying to access them, from this a proverb was born, "Like Hesky's library, all outside".
Content
Libraries, bookstores, and collections commonly divide books into fiction and non-fiction, though other types exist beyond this. Other books, which remain unpublished or are primarily published as part of different business functions (such as phone directories) may not be sold by bookstores or collected by libraries. Manuscripts, logbooks and other records may be classified and stored differently by special collections or archives.
Fiction
Fiction books contain invented material, typically narratives. Other literary forms such as poetry are included in the broad category. Most fiction is additionally categorized by literary form and genre.
The novel is the most common form of fiction book. Novels are extended works of narrative fiction, typically featuring a plot, setting, themes and characters. The novel has had a tremendous impact on entertainment and publishing markets. A novella is a term sometimes used for fiction prose typically between 17,500 and 40,000 words, and a novelette between 7,500 and 17,500. A short story may be any length up to 10,000 words, but these word lengths vary.
Comic books or graphic novels are books in which the story is illustrated. The characters and narrators use speech or thought bubbles to express verbal language.
Non-fiction | Book | Wikipedia | 504 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Non-fiction books are in principle based on fact, encompassing subjects such as history, politics, social and cultural issues, as well as autobiographies and memoirs. Nearly all academic literature is non-fiction.
Reference
Reference books are non-fiction books intended to be quickly referred to for information, rather than read beginning to end. The writing style used in these works is informative; the authors avoid opinions and the use of the first person, and emphasize facts.
An almanac is a very general reference book, usually one-volume, with lists of data and information on many topics. An encyclopedia is a book or set of books designed to have more in-depth articles on many topics. A book listing words, their etymology, meanings, and other information is called a dictionary. An atlas is a book containing a collection of maps. A specialized reference work giving information about a particular field or technique, often intended for professional use, is often called a handbook. Books which try to list references and abstracts in a certain broad area may be called an index, such as Engineering Index, or abstracts such as chemical abstracts and biological abstracts.
Technical
Books with technical information on how to do something or how to use some equipment are called instruction manuals. Other popular how-to books include cookbooks and home improvement books.
Educational
Students often carry textbooks and schoolbooks for study purposes. Lap books are a learning tool created by students. Elementary school pupils often use workbooks, which are published with spaces or blanks to be filled by them for study or homework. In US higher education, it is common for a student to take an exam using a blue book.
Religious
Religious texts, including scripture, are texts which various religions consider to be of central importance to their religious tradition. They often feature a compilation or discussion of beliefs, ritual practices, moral commandments and laws, ethical conduct, spiritual aspirations, and admonitions for fostering a religious community.
Hymnals are books with collections of musical hymns that can typically be found in churches. Prayerbooks or missals are books that contain written prayers and are commonly carried by monks, nuns, and other devoted followers or clergy.
Children's books
Unpublished
Many books are only used to record personal ideas, notes, and accounts, such as notebooks, logbooks, commonplace books, and diaries. These books are rarely published and are typically destroyed or remain private. | Book | Wikipedia | 483 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Address books, phone books, and calendar/appointment books are commonly used for recording appointments, meetings and personal contact information. Businesses historically used accounting books such as journals and ledgers to record financial data in a practice called bookkeeping (now usually held on computers rather than in hand-written form).
Collection and classification
Personal and public libraries, archives and other forms of book collection have led to the creation of many different organization and classification strategies. In the 19th and 20th century, libraries and library professionals systematized book collecting and classification systems to respond to the growing industry. The most widely used system is ISBN, which has provided unique identifiers for books since 1970.
Libraries
A library is a collection of books, and possibly other materials and media, that is accessible for use by its members and members of allied institutions. Libraries provide physical (hard copies) or digital (soft copies) materials, and may be a physical location, a virtual space, or both. A library's collection normally includes printed materials which may be borrowed, and usually also includes a reference section of publications which may only be utilized inside the premises. Resources such as commercial releases of films, television programs, other video recordings, radio, music and audio recordings may be available in many formats. These include DVDs, Blu-rays, CDs, cassettes, or other applicable formats such as microform. They may also provide access to information, music or other content held on bibliographic databases.
Libraries can vary widely in size and may be organized and maintained by a public body such as a government, an institution (such as a school or museum), a corporation, or a private individual. In addition to providing materials, libraries also provide the services of librarians who are trained experts in finding, selecting, circulating and organising information while interpreting information needs and navigating and analyzing large amounts of information with a variety of resources.
Library buildings often provide quiet areas for studying, as well as common areas for group study and collaboration, and may provide public facilities for access to their electronic resources, such as computers and access to the Internet.
The library's clientele and general services offered vary depending on its type: users of a public library have different needs from those of a special library or academic library, for example. Libraries may also be community hubs, where programs are made available and people engage in lifelong learning. Modern libraries extend their services beyond the physical walls of the building by providing material accessible by electronic means, including from home via the Internet.
Identification and classification | Book | Wikipedia | 510 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
In 2011, the International Federation of Library Associations and Institutions (IFLA) created the International Standard Bibliographic Description (ISBD) in order to standardize descriptions in bibliographies and library catalogs. Each book is specified by an International Standard Book Number, or ISBN, which is meant to be unique to every edition of every book produced by participating publishers, worldwide. It is managed by the ISBN Society. An ISBN has four parts: the first part is the country code, the second the publisher code, and the third the title code. The last part is a check digit, and can take values from 0–9 and X (10). The EAN Barcodes numbers for books are derived from the ISBN by prefixing 978, for Bookland, and calculating a new check digit.
Commercial publishers in industrialized countries generally assign ISBNs to their books, so buyers may presume that the ISBN is part of a total international system, with no exceptions. However, many government publishers, in industrial as well as developing countries, do not participate fully in the ISBN system, and publish books which do not have ISBNs. A large or public collection requires a catalogue. Codes called "call numbers" relate the books to the catalogue, and determine their locations on the shelves. Call numbers are based on a Library classification system. The call number is placed on the spine of the book, normally a short distance before the bottom, and inside. Institutional or national standards, such as ANSI/NISO Z39.41 – 1997, establish the correct way to place information (such as the title, or the name of the author) on book spines, and on "shelvable" book-like objects, such as containers for DVDs, video tapes and software.
One of the earliest and most widely known systems of cataloguing books is the Dewey Decimal System. Another widely known system is the Library of Congress Classification system. Both systems are biased towards subjects which were well represented in US libraries when they were developed, and hence have problems handling new subjects, such as computing, or subjects relating to other cultures. Information about books and authors can be stored in databases like online general-interest book databases. Metadata, which means "data about data" is information about a book. Metadata about a book may include its title, ISBN or other classification number (see above), the names of contributors (author, editor, illustrator) and publisher, its date and size, the language of the text, its subject matter, etc. | Book | Wikipedia | 512 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Classification systems
Bliss bibliographic classification (BC)
Chinese Library Classification (CLC)
Colon Classification
Dewey Decimal Classification (DDC)
Harvard-Yenching Classification
Library of Congress Classification (LCC)
New Classification Scheme for Chinese Libraries
Universal Decimal Classification (UDC)
Conservation
Social and cultural issues
Reception
The impact of books can be various, and record of that reception comes in several formats: starting with initial public reception in contemporary newspapers, pop culture and correspondence, and then developing over time with different forms of literary criticism by professional and academic critics. For the publishing industry the "book review" is an important part of increasing awareness and reception of a book: able to make or break the public opinion about a newly published book.
Book reviews
Book censorship and bans
Book censorship is the act of some authority taking measures to suppress ideas and information within a book. Censorship is "the regulation of free speech and other forms of entrenched authority". Censors typically identify as either a concerned parent, community members who react to a text without reading, or local or national organizations. Books have been censored by authoritarian dictatorships to silence dissent, such as the People's Republic of China, Nazi Germany and the Soviet Union. Books are most often censored for age appropriateness, offensive language, sexual content, amongst other reasons. Similarly, religions may issue lists of banned books, such as the historical example of the Catholic Church's Index Librorum Prohibitorum and bans of such books as Salman Rushdie's The Satanic Verses by Ayatollah Khomeini, which do not always carry legal force. Censorship can be enacted at the national or subnational level as well, and can carry legal penalties. In many cases, the authors of these books could face harsh sentences, exile from the country, or even execution.
Book burning | Book | Wikipedia | 374 | 3778 | https://en.wikipedia.org/wiki/Book | Technology | Media and communication | null |
Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The leaves are simple (although are sometimes deeply incised), lack stipules, and appear alternately on stems or in rosettes. The inflorescences are terminal and lack bracts. The flowers have four free sepals, four free alternating petals, two shorter free stamens and four longer free stamens. The fruit has seeds in rows, divided by a thin wall (or septum).
The family contains 372 genera and 4,060 accepted species. The largest genera are Draba (440 species), Erysimum (261 species), Lepidium (234 species), Cardamine (233 species), and Alyssum (207 species).
The family contains the cruciferous vegetables, including species such as Brassica oleracea (cultivated as cabbage, kale, cauliflower, broccoli and collards), Brassica rapa (turnip, Chinese cabbage, etc.), Brassica napus (rapeseed, etc.), Raphanus sativus (common radish), Armoracia rusticana (horseradish), but also a cut-flower Matthiola (stock) and the model organism Arabidopsis thaliana (thale cress).
Pieris rapae and other butterflies of the family Pieridae are some of the best-known pests of Brassicaceae species planted as commercial crops. Trichoplusia ni (cabbage looper) moth is also becoming increasingly problematic for crucifers due to its resistance to commonly used pest control methods. Some rarer Pieris butterflies, such as P. virginiensis, depend upon native mustards for their survival in their native habitats. Some non-native mustards such as Alliaria petiolata (garlic mustard), an extremely invasive species in the United States, can be toxic to their larvae.
Description | Brassicaceae | Wikipedia | 444 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Species belonging to the Brassicaceae are mostly annual, biennial, or perennial herbaceous plants, some are dwarf shrubs or shrubs, and very few vines. Although generally terrestrial, a few species such as water awlwort live submerged in fresh water. They may have a taproot or a sometimes woody caudex that may have few or many branches, some have thin or tuberous rhizomes, or rarely develop runners. Few species have multi-cellular glands. Hairs consist of one cell and occur in many forms: from simple to forked, star-, tree- or T-shaped, rarely taking the form of a shield or scale. They are never topped by a gland. The stems may be upright, rise up towards the tip, or lie flat, are mostly herbaceous but sometimes woody. Stems carry leaves or the stems may be leafless (in Caulanthus), and some species lack stems altogether. The leaves do not have stipules, but there may be a pair of glands at base of leaf stalks and flower stalks. The leaf may be seated or have a leafstalk. The leaf blade is usually simple, entire or dissected, rarely trifoliolate or pinnately compound. A leaf rosette at the base may be present or absent. The leaves along the stem are almost always alternately arranged, rarely apparently opposite. The stomata are of the anisocytic type. The genome size of Brassicaceae compared to that of other Angiosperm families is very small to small (less than 3.425 million base pairs per cell), varying from 150 Mbp in Arabidopsis thaliana and Sphaerocardamum spp., to 2375 Mbp Bunias orientalis. The number of homologous chromosome sets varies from four (n=4) in some Physaria and Stenopetalum species, five (n=5) in other Physaria and Stenopetalum species, Arabidopsis thaliana and a Mathiola species, to seventeen (n=17). About 35% of the species in which chromosomes have been counted have eight sets (n=8). Due to polyploidy, some species may have up to 256 individual chromosomes, with some very high counts in the North American species of Cardamine, such as C. diphylla | Brassicaceae | Wikipedia | 488 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Hybridisation is not unusual in Brassicaceae, especially in Arabis, Rorippa, Cardamine and Boechera. Hybridisation between species originating in Africa and California, and subsequent polyploidisation is surmised for Lepidium species native to Australia and New Zealand | Brassicaceae | Wikipedia | 57 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Inflorescence and flower
Flowers may be arranged in racemes, panicles, or corymbs, with pedicels sometimes in the axil of a bract, and few species have flowers that sit individually on flower stems that spring from the axils of rosette leaves. The orientation of the pedicels when fruits are ripe varies dependent on the species. The flowers are bisexual, star symmetrical (zygomorphic in Iberis and Teesdalia) and the ovary positioned above the other floral parts. Each flower has four free or seldom merged sepals, the lateral two sometimes with a shallow spur, which are mostly shed after flowering, rarely persistent, may be reflexed, spreading, ascending, or erect, together forming a tube-, bell- or urn-shaped calyx. Each flower has four petals, set alternating with the sepals, although in some species these are rudimentary or absent. They may be differentiated into a blade and a claw or not, and consistently lack basal appendages. The blade is entire or has an indent at the tip, and may sometimes be much smaller than the claws. The mostly six stamens are set in two whorls: usually the two lateral, outer ones are shorter than the four inner stamens, but very rarely the stamens can all have the same length, and very rarely species have different numbers of stamens such as sixteen to twenty four in Megacarpaea, four in Cardamine hirsuta, and two in Coronopus. The filaments are slender and not fused, while the anthers consist of two pollen producing cavities, and open with longitudinal slits. The pollen grains are tricolpate. The receptacle carries a variable number of nectaries, but these are always present opposite the base of the lateral stamens. | Brassicaceae | Wikipedia | 377 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Ovary, fruit and seed
There is one superior pistil that consists of two carpels that may either sit directly above the base of the stamens or on a stalk. It initially consists of only one cavity but during its further development a thin wall grows that divides the cavity, both placentas and separates the two valves (a so-called false septum). Rarely, there is only one cavity without a septum. The 2–600 ovules are usually along the side margin of the carpels, or rarely at the top. Fruits are capsules that open with two valves, usually towards the top. These are called silique if at least three times longer than wide, or silicle if the length is less than three times the width. The fruit is very variable in its other traits. There may be one persistent style that connects the ovary to the globular or conical stigma, which is undivided or has two spreading or connivent lobes. The variously shaped seeds are usually yellow or brown in color, and arranged in one or two rows in each cavity. The seed leaves are entire or have a notch at the tip. The seed does not contain endosperm.
Differences with similar families
Brassicaceae have a bisymmetrical corolla (left is mirrored by right, stem-side by out-side, but each quarter is not symmetrical), a septum dividing the fruit, lack stipules and have simple (although sometimes deeply incised) leaves. The sister family Cleomaceae has bilateral symmetrical corollas (left is mirrored by right, but stem-side is different from out-side), stipules and mostly palmately divided leaves, and mostly no septum. Capparaceae generally have a gynophore, sometimes an androgynophore, and a variable number of stamens. | Brassicaceae | Wikipedia | 390 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Phytochemistry
Almost all Brassicaceae have C3 carbon fixation. The only exceptions are a few Moricandia species, which have a hybrid system between C3 and C4 carbon fixation, C4 fixation being more efficient in drought, high temperature and low nitrate availability. Brassicaceae contain different cocktails of dozens of glucosinolates. They also contain enzymes called myrosinases, that convert the glucosinolates into isothiocyanates, thiocyanates and nitriles, which are toxic to many organisms, and so help guard against herbivory.
Taxonomy
Carl Linnaeus in 1753 regarded the Brassicaceae as a natural group, naming them "Klass" Tetradynamia. Alfred Barton Rendle placed the family in the order Rhoeadales, while George Bentham and Joseph Dalton Hooker in their system published from 1862 to 1883, assigned it to their cohort Parietales (now the class Violales). Following Bentham and Hooker, John Hutchinson in 1948 and again in 1964 thought the Brassicaceae to stem from near the Papaveraceae. In 1994, a group of scientists including Walter Stephen Judd suggested to include the Capparaceae in the Brassicaceae. Early DNA-analysis showed that the Capparaceae—as defined at that moment—were paraphyletic, and it was suggested to assign the genera closest to the Brassicaceae to the Cleomaceae. The Cleomaceae and Brassicaceae diverged approximately 41 million years ago. All three families have consistently been placed in one order (variably called Capparales or Brassicales). The APG II system merged Cleomaceae and Brassicaceae. Other classifications have continued to recognize the Capparaceae, but with a more restricted circumscription, either including Cleome and its relatives in the Brassicaceae or recognizing them in the segregate family Cleomaceae. The APG III system has recently adopted this last solution, but this may change as a consensus arises on this point. Current insights in the relationships of the Brassicaceae, based on a 2012 DNA-analysis, are summarized in the following tree. | Brassicaceae | Wikipedia | 459 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Relationships within the family
Early classifications depended on morphological comparison only, but because of extensive convergent evolution, these do not provide a reliable phylogeny. Although a substantial effort was made through molecular phylogenetic studies, the relationships within the Brassicaceae have not always been well resolved yet. It has long been clear that the Aethionema are sister of the remainder of the family. One analysis from 2014 represented the relation between 39 tribes with the following tree.
Genera
As of October 2023 Plants of the World Online accepts 346 genera.
Etymology
The name Brassicaceae comes to international scientific vocabulary from Neo-Latin, from Brassica, the type genus, + -aceae, a standardized suffix for plant family names in modern taxonomy. The genus name comes from the Classical Latin word brassica, referring to cabbage and other cruciferous vegetables. The alternative older name, Cruciferae, meaning "cross-bearing", describes the four petals of mustard flowers, which resemble a cross. Cruciferae is one of eight plant family names, not derived from a genus name and without the suffix -aceae that are authorized alternative names.
Distribution
Brassicaceae can be found almost on the entire land surface of the planet, but the family is absent from Antarctica, and also absent from some areas in the tropics i.e. northeastern Brazil, the Congo basin, Maritime Southeast Asia and tropical Australasia. The area of origin of the family is possibly the Irano-Turanian region, where approximately 900 species occur in 150 different genera. About 530 of those 900 species are endemics. Next in abundance comes the Mediterranean region, with around 630 species (290 of which are endemic) in 113 genera. The family is less prominent in the Saharo-Arabian region—65 genera, 180 species of which 62 are endemic—and North America (comprising the North American Atlantic region and the Rocky Mountain floristic region)—99 genera, 780 species of which 600 are endemic. South America has 40 genera containing 340 native species, Southern Africa 15 genera with over 100 species, and Australia and New-Zealand have 19 genera with 114 species between them. | Brassicaceae | Wikipedia | 438 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Ecology
Brassicaceae are almost exclusively pollinated by insects. A chemical mechanism in the pollen is active in many species to avoid selfing. Two notable exceptions are exclusive self-pollination in closed flowers in Cardamine chenopodifolia, and wind pollination in Pringlea antiscorbutica. Although it can be cross-pollinated, Alliaria petiolata (garlic mustard) is self-fertile. Most species reproduce sexually through seed, but Cardamine bulbifera produces gemmae and in others, such as Cardamine pentaphyllos, the coral-like roots easily break into segments, that will grow into separate plants. In some species, such as in the genus Cardamine, seed pods open with force and so catapult the seeds quite far. Many of these have sticky seed coats, assisting long-distance dispersal by animals, and this may also explain several intercontinental dispersal events in the genus, and its near global distribution. Brassicaceae are common on serpentine and dolomite rich in magnesium. Over a hundred species in the family accumulate heavy metals, particularly zinc and nickel, which is a record percentage. Several Alyssum species can accumulate nickel up to 0.3% of their dry weight, and may be useful in soil remediation or even bio-mining. | Brassicaceae | Wikipedia | 267 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Brassicaceae contain glucosinolates as well as myrosinases inside their cells. When the cell is damaged, the myrosinases hydrolise the glucosinolates, leading to the synthesis of isothiocyanates, which are compounds toxic to most animals, fungi and bacteria. Some insect herbivores have developed counter adaptations such as rapid absorption of the glucosinates, quick alternative breakdown into non-toxic compounds and avoiding cell damage. In the whites family (Pieridae), one counter mechanism involves glucosinolate sulphatase, which changes the glucosinolate, so that it cannot be converted to isothiocyanate. A second is that the glucosinates are quickly broken down, forming nitriles. Differences between the mixtures of glucosinolates between species and even within species is large, and individual plants may produce in excess of fifty individual substances. The energy penalty for synthesising all these glucosinolates may be as high as 15% of the total needed to produce a leaf. Barbarea vulgaris (bittercress) also produces triterpenoid saponins. These adaptations and counter adaptations probably have led to extensive diversification in both the Brassicaceae and one of its major pests, the butterfly family Pieridae. A particular cocktail of volatile glucosinates triggers egg-laying in many species. Thus a particular crop can sometimes be protected by planting bittercress as a deadly bait, for the saponins kill the caterpillars, but the butterfly is still lured by the bittercress to lay its egg on the leaves.
A moth that feeds on a range of Brassicaceae is the diamondback moth (Plutella xylostella). Like the Pieridae, it is capable of converting isothiocyanates into less problematic nitriles. Managing this pest in crops became more complicated after resistance developed against a toxin produced by Bacillus thuringiensis, which is used as a wide spectrum biological plant protection against caterpillars. Parasitoid wasps that feed on such insect herbivores are attracted to the chemical compounds released by the plants, and thus are able to locate their prey. The cabbage aphid (Brevicoryne brassicae) stores glucosinolates and synthesises its own myrosinases, which may deter its potential predators. | Brassicaceae | Wikipedia | 494 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Since its introduction in the 19th century, Alliaria petiolata has been shown to be extremely successful as an invasive species in temperate North America due, in part, to its secretion of allelopathic chemicals. These inhibit the germination of most competing plants and kill beneficial soil fungi needed by many plants, such as many tree species, to successfully see their seedlings grow to maturity. The monoculture formation of an herb layer carpet by this plant has been shown to dramatically alter forests, making them wetter, having fewer and fewer trees, and having more vines such as poison ivy (Toxicodendron radicans). The overall herb layer biodiversity is also drastically reduced, particularly in terms of sedges and forbs. Research has found that removing 80% of the garlic mustard infestation plants did not lead to a particularly significant recovery of that diversity. Instead, it required around 100% removal. Given that not one of an estimated 76 species that prey on the plant has been approved for biological control in North America and the variety of mechanisms the plant has to ensure its dominance without them (e.g. high seed production, self-fertility, allelopathy, spring growth that occurs before nearly all native plants, roots that break easily when pulling attempts are made, a complete lack of palatability for herbivores at all life stages, etc.) it is unlikely that such a high level of control can be established and maintained on the whole. It is estimated that adequate control can be achieved with the introduction of two European weevils, including one that is monophagous. The USDA's TAG group has blocked these introductions since 2004. In addition to being invasive, garlic mustard also is a threat to native North American Pieris butterflies such as P. oleracea, as they preferentially oviposit on it, although it is toxic to their larvae.
Invasive aggressive mustard species are known for being self-fertile, seeding very heavily with small seeds that have a lengthy lifespan coupled with a very high rate of viability and germination, and for being completely unpalatable to both herbivores and insects in areas to which they are not native. Garlic mustard is toxic to several rarer North American Pieris species.
Uses | Brassicaceae | Wikipedia | 463 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
This family includes important agricultural crops, among which many vegetables such as cabbage, broccoli, cauliflower, kale, Brussels sprouts, collard greens, Savoy, kohlrabi, and gai lan (Brassica oleracea), turnip, napa cabbage, mizuna, bok choy and rapini (Brassica rapa), rocket salad/arugula (Eruca sativa), garden cress (Lepidium sativum), watercress (Nasturtium officinale) and radish (Raphanus) and a few spices like horseradish (Armoracia rusticana), wasabi (Eutrema japonicum), white, Indian and black mustard (Sinapis alba, Brassica juncea and B. nigra respectively). Vegetable oil is produced from the seeds of several species such as Brassica napus (rapeseed oil), perhaps providing the largest volume of vegetable oils of any species. Woad (Isatis tinctoria) was used in the past to produce a blue textile dye (indigo), but has largely been replaced by the same substance from unrelated tropical species like Indigofera tinctoria.
Pringlea antiscorbutica, commonly known as Kerguelen cabbage, is edible, containing high levels of potassium. Its leaves contain a vitamin C-rich oil, a fact which, in the days of sailing ships, made it very attractive to sailors suffering from scurvy, hence the species name's epithet antiscorbutica, which means "against scurvy" in Low Latin. It was essential to the diets of the whalers on Kerguelen when pork, beef, or seal meat was used up.
The Brassicaceae also includes ornamentals, such as species of Aethionema, Alyssum, Arabis, Aubrieta, Aurinia, Cheiranthus, Erysimum, Hesperis, Iberis, Lobularia, Lunaria, Malcolmia, and Matthiola. Honesty (Lunaria annua) is cultivated for the decorative value of the translucent remains of the fruits after drying. It can be a pest species in areas where it is not native.
The small Eurasian weed Arabidopsis thaliana is widely used as model organism in the study of the molecular biology of flowering plants (Angiospermae). | Brassicaceae | Wikipedia | 504 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
Some species are useful as food plants for Lepidoptera, such as certain wild mustard and cress species, such as Turritis glabra and Boechera laevigata that are utilized by several North American butterflies.
Gallery | Brassicaceae | Wikipedia | 48 | 3794 | https://en.wikipedia.org/wiki/Brassicaceae | Biology and health sciences | Brassicales | null |
In probability theory and statistics, the binomial distribution with parameters and is the discrete probability distribution of the number of successes in a sequence of independent experiments, each asking a yes–no question, and each with its own Boolean-valued outcome: success (with probability ) or failure (with probability ). A single success/failure experiment is also called a Bernoulli trial or Bernoulli experiment, and a sequence of outcomes is called a Bernoulli process; for a single trial, i.e., , the binomial distribution is a Bernoulli distribution. The binomial distribution is the basis for the binomial test of statistical significance.
The binomial distribution is frequently used to model the number of successes in a sample of size drawn with replacement from a population of size . If the sampling is carried out without replacement, the draws are not independent and so the resulting distribution is a hypergeometric distribution, not a binomial one. However, for much larger than , the binomial distribution remains a good approximation, and is widely used.
Definitions
Probability mass function
If the random variable follows the binomial distribution with parameters and , we write . The probability of getting exactly successes in independent Bernoulli trials (with the same rate ) is given by the probability mass function:
for , where
is the binomial coefficient. The formula can be understood as follows: is the probability of obtaining the sequence of independent Bernoulli trials in which trials are "successes" and the remaining trials result in "failure". Since the trials are independent with probabilities remaining constant between them, any sequence of trials with successes (and failures) has the same probability of being achieved (regardless of positions of successes within the sequence). There are such sequences, since the binomial coefficient counts the number of ways to choose the positions of the successes among the trials. The binomial distribution is concerned with the probability of obtaining any of these sequences, meaning the probability of obtaining one of them () must be added times, hence .
In creating reference tables for binomial distribution probability, usually, the table is filled in up to values. This is because for , the probability can be calculated by its complement as
Looking at the expression as a function of , there is a value that maximizes it. This value can be found by calculating
and comparing it to 1. There is always an integer that satisfies | Binomial distribution | Wikipedia | 493 | 3876 | https://en.wikipedia.org/wiki/Binomial%20distribution | Mathematics | Statistics and probability | null |
is monotone increasing for and monotone decreasing for , with the exception of the case where is an integer. In this case, there are two values for which is maximal: and . is the most probable outcome (that is, the most likely, although this can still be unlikely overall) of the Bernoulli trials and is called the mode.
Equivalently, . Taking the floor function, we obtain .
Example
Suppose a biased coin comes up heads with probability 0.3 when tossed. The probability of seeing exactly 4 heads in 6 tosses is
Cumulative distribution function
The cumulative distribution function can be expressed as:
where is the "floor" under , i.e. the greatest integer less than or equal to .
It can also be represented in terms of the regularized incomplete beta function, as follows:
which is equivalent to the cumulative distribution functions of the beta distribution and of the -distribution:
Some closed-form bounds for the cumulative distribution function are given below.
Properties
Expected value and variance
If , that is, is a binomially distributed random variable, being the total number of experiments and p the probability of each experiment yielding a successful result, then the expected value of is:
This follows from the linearity of the expected value along with the fact that is the sum of identical Bernoulli random variables, each with expected value . In other words, if are identical (and independent) Bernoulli random variables with parameter , then and
The variance is:
This similarly follows from the fact that the variance of a sum of independent random variables is the sum of the variances.
Higher moments
The first 6 central moments, defined as , are given by
The non-central moments satisfy
and in general
where are the Stirling numbers of the second kind, and is the th falling power of .
A simple bound
follows by bounding the Binomial moments via the higher Poisson moments:
This shows that if , then is at most a constant factor away from
Mode
Usually the mode of a binomial distribution is equal to , where is the floor function. However, when is an integer and is neither 0 nor 1, then the distribution has two modes: and . When is equal to 0 or 1, the mode will be 0 and correspondingly. These cases can be summarized as follows:
Proof: Let
For only has a nonzero value with . For we find and for . This proves that the mode is 0 for and for .
Let . We find
.
From this follows | Binomial distribution | Wikipedia | 496 | 3876 | https://en.wikipedia.org/wiki/Binomial%20distribution | Mathematics | Statistics and probability | null |
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