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Like oil and water, a molten metal may not always mix with another element. For example, pure iron is almost completely insoluble with copper. Even when the constituents are soluble, each will usually have a saturation point, beyond which no more of the constituent can be added. Iron, for example, can hold a maximum of... | Wikipedia - Alloy - Characteristics | 350 | 1,700 | null |
Bronze was an extremely useful alloy to the ancients, because it is much stronger and harder than either of its components. Steel was another common alloy. However, in ancient times, it could only be created as an accidental byproduct from the heating of iron ore in fires (smelting) during the manufacture of iron. Othe... | Wikipedia - Alloy - Characteristics | 335 | 1,573 | null |
Section: Theory. Alloying a metal is done by combining it with one or more other elements. The most common and oldest alloying process is performed by heating the base metal beyond its melting point and then dissolving the solutes into the molten liquid, which may be possible even if the melting point of the solute is ... | Wikipedia - Alloy - Theory | 328 | 1,461 | null |
It may also be done with one, more, or all of the constituents in the solid state, such as found in ancient methods of pattern welding (solid-solid), shear steel (solid-solid), or crucible steel production (solid-liquid), mixing the elements via solid-state diffusion. By adding another element to a metal, differences i... | Wikipedia - Alloy - Theory | 331 | 1,628 | null |
Section: Theory > Heat treatment. Alloying elements are added to a base metal, to induce hardness, toughness, ductility, or other desired properties. Most metals and alloys can be work hardened by creating defects in their crystal structure. These defects are created during plastic deformation by hammering, bending, ex... | Wikipedia - Alloy - Theory > Heat treatment | 311 | 1,477 | null |
If the steel is cooled slowly, the carbon can diffuse out of the iron and it will gradually revert to its low temperature allotrope. During slow cooling, the carbon atoms will no longer be as soluble with the iron, and will be forced to precipitate out of solution, nucleating into a more concentrated form of iron carbi... | Wikipedia - Alloy - Theory > Heat treatment | 349 | 1,613 | null |
The solutes in these alloys will precipitate over time, forming intermetallic phases, which are difficult to discern from the base metal. Unlike steel, in which the solid solution separates into different crystal phases (carbide and ferrite), precipitation hardening alloys form different phases within the same crystal.... | Wikipedia - Alloy - Theory > Heat treatment | 328 | 1,615 | null |
Section: Theory > Mechanisms. When a molten metal is mixed with another substance, there are two mechanisms that can cause an alloy to form, called atom exchange and the interstitial mechanism. The relative size of each element in the mix plays a primary role in determining which mechanism will occur. When the atoms ar... | Wikipedia - Alloy - Theory > Mechanisms | 268 | 1,374 | null |
Section: History and examples > Bronze and brass. Iron is usually found as iron ore on Earth, except for one deposit of native iron in Greenland, which was used by the Inuit. Native copper, however, was found worldwide, along with silver, gold, and platinum, which were also used to make tools, jewelry, and other object... | Wikipedia - Alloy - History and examples > Bronze and brass | 271 | 1,340 | null |
Section: History and examples > Precious metals. Many ancient civilizations alloyed metals for purely aesthetic purposes. In ancient Egypt and Mycenae, gold was often alloyed with copper to produce red-gold, or iron to produce a bright burgundy-gold. Gold was often found alloyed with silver or other metals to produce v... | Wikipedia - Alloy - History and examples > Precious metals | 185 | 899 | null |
Section: History and examples > Pewter. The term pewter covers a variety of alloys consisting primarily of tin. As a pure metal, tin is much too soft to use for most practical purposes. However, during the Bronze Age, tin was a rare metal in many parts of Europe and the Mediterranean, so it was often valued higher than... | Wikipedia - Alloy - History and examples > Pewter | 254 | 1,194 | null |
Section: History and examples > Iron. The first known smelting of iron began in Anatolia, around 1800 BC. Called the bloomery process, it produced very soft but ductile wrought iron. By 800 BC, iron-making technology had spread to Europe, arriving in Japan around 700 AD. Pig iron, a very hard but brittle alloy of iron ... | Wikipedia - Alloy - History and examples > Iron | 335 | 1,573 | null |
The ability to modify the hardness of steel by heat treatment had been known since 1100 BC, and the rare material was valued for the manufacture of tools and weapons. Because the ancients could not produce temperatures high enough to melt iron fully, the production of steel in decent quantities did not occur until the ... | Wikipedia - Alloy - History and examples > Iron | 348 | 1,747 | null |
Steel is an alloy of iron and carbon, but the term alloy steel usually only refers to steels that contain other elements— like vanadium, molybdenum, or cobalt—in amounts sufficient to alter the properties of the base steel. Since ancient times, when steel was used primarily for tools and weapons, the methods of produci... | Wikipedia - Alloy - History and examples > Iron | 331 | 1,703 | null |
Afterward, many people began experimenting with various alloys of steel without much success. However, in 1882, Robert Hadfield, being a pioneer in steel metallurgy, took an interest and produced a steel alloy containing around 12% manganese. Called mangalloy, it exhibited extreme hardness and toughness, becoming the f... | Wikipedia - Alloy - History and examples > Iron | 296 | 1,371 | null |
Section: History and examples > Others. Due to their high reactivity, most metals were not discovered until the 19th century. A method for extracting aluminium from bauxite was proposed by Humphry Davy in 1807, using an electric arc. Although his attempts were unsuccessful, by 1855 the first sales of pure aluminium rea... | Wikipedia - Alloy - History and examples > Others | 331 | 1,658 | null |
Section: History > Origins. Amateur chemistry shares its early history with that of chemistry in general. Pioneers of modern chemistry such as Robert Boyle and Antoine Lavoisier were gentlemen scientists who pursued their research independently from their source of income. Only with the coming of the Industrial Revolut... | Wikipedia - Amateur chemistry - History > Origins | 220 | 1,212 | null |
Section: History > Chemistry as a hobby. Throughout much of the 20th century, amateur chemistry was an unexceptional hobby, with high-quality chemistry sets readily available, and laboratory suppliers freely selling to hobbyists. For example, Linus Pauling had no difficulty in procuring potassium cyanide at the age of ... | Wikipedia - Amateur chemistry - History > Chemistry as a hobby | 256 | 1,262 | null |
Section: Notable amateur chemists. Internet pioneer Vint Cerf, Intel co-founder Gordon Moore, and Hewlett Packard co-founder David Packard all used to practice amateur chemistry. British neurologist Oliver Sacks was a keen amateur chemist in his youth, as described in his memoir Uncle Tungsten: Memories of a Chemical B... | Wikipedia - Amateur chemistry - Notable amateur chemists | 333 | 1,741 | null |
Section: Restrictions. Whilst the hobby is probably legal in most jurisdictions,[b] the relationship between amateur chemists and law enforcement agencies is often fraught. Hobbyists are often affected by laws intended to fight drugs and terrorism. Furthermore, many chemical supply houses refuse to sell to amateurs, wi... | Wikipedia - Amateur chemistry - Restrictions | 156 | 922 | null |
Section: Restrictions > Canada. In Canada, a wide range of basic laboratory reagents such as nitric acid and hydrogen peroxide are restricted as "explosives precursors". Two of the main legal texts in Canada restricting the sale of certain chemicals are the Explosives Act, and the Explosives Regulations, 2013 (SOR/2013... | Wikipedia - Amateur chemistry - Restrictions > Canada | 303 | 1,369 | null |
Section: Restrictions > European Union. In the EU, regulations regarding reagent restrictions can be classified in several different sets: dual-use goods, substances in the Schedules 1, 2 and 3 of the CWC, substances on the Common Military List, hazardous chemicals (as defined by Prior Informed Consent Regulation), che... | Wikipedia - Amateur chemistry - Restrictions > European Union | 345 | 1,761 | null |
Any individual can own these chemicals provided their concentration is below or equal to a given limit (e.g. for sulfuric acid up to 15% conc. in weight). Said upper limit allowed can be increased (e.g. for sulfuric acid, up to 40% conc.) by requesting a license to the national authority. Professional users are not aff... | Wikipedia - Amateur chemistry - Restrictions > European Union | 350 | 1,656 | null |
These codes were defined by the Commission Decision 2000/532/EC, later amended by Commission Decision 2014/955/EU. Laboratories typically classify their wastes into those containing halogenated solvents (such as chloroform and dichloromethane, EWC 14 06 02), non-halogenated solvents (like hexane and toluene, EWC 14 06 ... | Wikipedia - Amateur chemistry - Restrictions > European Union | 239 | 920 | null |
Both Council Directive 92/81/EEC, and Council Directive 2003/96/EC, which repealed the former, impose taxes on several hydrocarbons that can be used as fuels. These hydrocarbons include hexane, heptane, isooctane (CN 2901 10 for most saturated acyclic hydrocarbons), petroleum ether (CN 2710 12 25), cyclohexane (CN 2902... | Wikipedia - Amateur chemistry - Restrictions > European Union | 167 | 502 | null |
Section: Restrictions > European Union > Germany. Regulations regarding hazardous chemicals in this country include the Explosives Act (Sprengstoffgesetz), and the Hazardous Substances Ordinance (Gefahrstoffverordnung, abbreviated as GefStoffV), which is part of the Chemicals Act (Chemikaliengesetz, abbreviated as Chem... | Wikipedia - Amateur chemistry - Restrictions > European Union > Germany | 166 | 704 | null |
Section: Restrictions > European Union > Italy. In Italy, regulations regarding explosives precursors have been approved as the Ministry of the Interior's Circolare 557/PAS/U/004997/XV.H.MASS(53)5, titled Identificazione e tracciabilità degli esplosivi per uso civile: - Indicazioni operative e gestione delle scorte. Re... | Wikipedia - Amateur chemistry - Restrictions > European Union > Italy | 155 | 549 | null |
Section: Restrictions > European Union > Spain. Since the 1940s, chemistry sets for kids have been available on the Spanish market, some of these including "Quimicefa", manufactured by the Valencian company Celulosa Fabril SA (CEFA), and later on by CEFA Toys SA; "Cheminova", by Jugetes Mediterráneo SA, from Aldaia, Va... | Wikipedia - Amateur chemistry - Restrictions > European Union > Spain | 346 | 1,415 | null |
By the 2010s, many of them were no longer available. Despite these incidents, the positive impact of chemistry sets on kickstarting the curiosity of children, some of whom would later become professional scientists and engineers, has been acknowledged. According to the Resolution of 20 November 2013 of the Spanish Stat... | Wikipedia - Amateur chemistry - Restrictions > European Union > Spain | 321 | 1,530 | null |
The first ones (purchases and sales) must include information on the quantities, full contact details and address, and NIF or DNI number of the suppliers or buyers. Additionally, the storage of chemicals, including reagents, flammable solvents, and gas cylinders, is regulated by Royal Decree 656/2017, of 23 June. Indus... | Wikipedia - Amateur chemistry - Restrictions > European Union > Spain | 316 | 1,487 | null |
According to article 79 of the latter, even though ethanol is subject to a special tax due to its potential use in spirits, its use in scientific research can be exempted. This exemption requires obtaining an Activity and Establishment Code (Código de Actividad y del Establecimiento, CAE), which allows to request a ref... | Wikipedia - Amateur chemistry - Restrictions > European Union > Spain | 188 | 848 | null |
Section: Restrictions > Norway. In September 2018, a 29-year-old physician and amateur chemist and his girlfriend were arrested at their home on in Nord-Jæren, two days after inquiring a local pharmacy about the availability of 35% hydrogen peroxide. He explained that he had an accident while camping, suffering a wound... | Wikipedia - Amateur chemistry - Restrictions > Norway | 196 | 892 | null |
Section: Restrictions > United Kingdom. In the UK it is a criminal offence for members of the general public to purchase, and for business to sell, certain types of poisons or explosives precursors to those of the former group without a valid EPP license. Purchasing substances on this list is restricted since 26 May 20... | Wikipedia - Amateur chemistry - Restrictions > United Kingdom | 285 | 1,408 | null |
On 1 October 2023, a new set of amendments to the Poisons Act 1972, known as the "Control of Poisons and Explosives Precursors Regulations 2023", came into force. According to these amendments, hexamine, hydrochloric acid in concentrations 10% w/w and higher, and ammonium nitrate with a nitrogen content of 16% or highe... | Wikipedia - Amateur chemistry - Restrictions > United Kingdom | 247 | 1,066 | null |
Section: Restrictions > United States. In the United States, the Drug Enforcement Administration maintains lists regarding the classification of illicit drugs, which contain chemicals that are used to manufacture the controlled substances/illicit drugs. The lists are designated within The Controlled Substances Act, 21 ... | Wikipedia - Amateur chemistry - Restrictions > United States | 312 | 1,541 | null |
In 2008, the home laboratory of Victor Deeb, a retired chemist, was raided and dismantled Almost a year later, Jack Robison, then a 19-year-old chemistry student at the Holyoke Community College, received a visit from members of the Massachusetts State Police, the Bureau of Alcohol, Tobacco, Firearms and Explosives, an... | Wikipedia - Amateur chemistry - Restrictions > United States | 157 | 794 | null |
Section: History > History of spectroscopy. Observations of solar spectra as performed by Athanasius Kircher (1646), Jan Marek Marci (1648), Robert Boyle (1664), and Francesco Maria Grimaldi (1665) all predated Newton's 1666 work which established the spectral nature of light and resulted in the first spectroscope. Spe... | Wikipedia - Astrochemistry - History > History of spectroscopy | 339 | 1,770 | null |
Section: History > History of astrochemistry. While radio astronomy was developed in the 1930s, it was not until 1937 that any substantial evidence arose for the conclusive identification of an interstellar molecule – up until this point, the only chemical species known to exist in interstellar space were atomic. These... | Wikipedia - Astrochemistry - History > History of astrochemistry | 304 | 1,583 | null |
Section: Spectroscopy. One particularly important experimental tool in astrochemistry is spectroscopy through the use of telescopes to measure the absorption and emission of light from molecules and atoms in various environments. By comparing astronomical observations with laboratory measurements, astrochemists can inf... | Wikipedia - Astrochemistry - Spectroscopy | 313 | 1,665 | null |
The radio observation of perhaps greatest human interest is the claim of interstellar glycine, the simplest amino acid, but with considerable accompanying controversy. One of the reasons why this detection was controversial is that although radio (and some other methods like rotational spectroscopy) are good for the id... | Wikipedia - Astrochemistry - Spectroscopy | 350 | 1,632 | null |
NASA's researchers use airborne IR telescope SOFIA and space telescope Spitzer for their observations, researches and scientific operations. Somewhat related to the recent detection of methane in the atmosphere of Mars. Christopher Oze, of the University of Canterbury in New Zealand and his colleagues reported, in June... | Wikipedia - Astrochemistry - Spectroscopy | 317 | 1,510 | null |
The PAHs are thought to form in hot circumstellar environments (around dying, carbon-rich red giant stars). Infrared astronomy has also been used to assess the composition of solid materials in the interstellar medium, including silicates, kerogen-like carbon-rich solids, and ices. This is because unlike visible light,... | Wikipedia - Astrochemistry - Spectroscopy | 327 | 1,601 | null |
Section: Research. Research is progressing on the way in which interstellar and circumstellar molecules form and interact, e.g. by including non-trivial quantum mechanical phenomena for synthesis pathways on interstellar particles. This research could have a profound impact on our understanding of the suite of molecule... | Wikipedia - Astrochemistry - Research | 335 | 1,807 | null |
Molecular spectroscopy allows us to see these stars transitioning from an original composition in which oxygen was more abundant than carbon, to a carbon star phase where the carbon produced by helium burning is brought to the surface by deep convection, and dramatically changes the molecular content of the stellar win... | Wikipedia - Astrochemistry - Research | 297 | 1,445 | null |
In September, 2012, NASA scientists reported that polycyclic aromatic hydrocarbons (PAHs), subjected to interstellar medium (ISM) conditions, are transformed, through hydrogenation, oxygenation and hydroxylation, to more complex organics – "a step along the path toward amino acids and nucleotides, the raw materials of ... | Wikipedia - Astrochemistry - Research | 350 | 1,593 | null |
For the study of the recourses of chemical elements and molecules in the universe is developed the mathematical model of the molecules composition distribution in the interstellar environment on thermodynamic potentials by professor M.Yu. Dolomatov using methods of the probability theory, the mathematical and physical ... | Wikipedia - Astrochemistry - Research | 322 | 1,588 | null |
Section: History. The first scientific studies of atmospheric composition began in the 18th century when chemists such as Joseph Priestley, Antoine Lavoisier and Henry Cavendish made the first measurements of the composition of the atmosphere. In the late 19th and early 20th centuries, researchers shifted their interes... | Wikipedia - Atmospheric chemistry - History | 344 | 1,873 | null |
Section: Methodology > Observation. Field observations of chemical systems are essential to understanding atmospheric processes and determining the accuracy of models. Atmospheric chemistry measurements are long term to observe continuous trends or short term to observe smaller variations. In situ and remote measuremen... | Wikipedia - Atmospheric chemistry - Methodology > Observation | 270 | 1,598 | null |
Section: Methodology > Laboratory studies. Laboratory studies help understand the complex interactions from Earth’s systems that can be difficult to measure on a large scale. Experiments are performed in controlled environments, such as aerosol chambers, that allow for the individual evaluation of specific chemical rea... | Wikipedia - Atmospheric chemistry - Methodology > Laboratory studies | 200 | 1,085 | null |
Section: Methodology > Modeling. Models are essential tools for interpreting observational data, testing hypotheses about chemical reactions, and predicting future concentrations of atmospheric chemicals. To synthesize and test theoretical understanding of atmospheric chemistry, researchers commonly use computer models... | Wikipedia - Atmospheric chemistry - Methodology > Modeling | 337 | 1,978 | null |
This makes them useful for studying specific chemical reactions, but limited in stimulating real-world dynamics. In contrast, 3D models are more complex, representing a variety of physical processes such as wind, convection, and atmospheric mixing. They also provide more realistic representations of transportation and ... | Wikipedia - Atmospheric chemistry - Methodology > Modeling | 339 | 2,073 | null |
Section: Applications. Atmospheric chemistry is a multidisciplinary field with wide-ranging applications that influence environmental policy, human health, technology development, and climate science. Examples of problems addressed in atmospheric chemistry include acid rain, ozone depletion, photochemical smog, greenho... | Wikipedia - Atmospheric chemistry - Applications | 301 | 1,767 | null |
Article: Atom. Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, an... | Wikipedia - Atom - Summary | 332 | 1,630 | null |
The electrons of an atom are attracted to the protons in an atomic nucleus by the electromagnetic force. The protons and neutrons in the nucleus are attracted to each other by the nuclear force. This force is usually stronger than the electromagnetic force that repels the positively charged protons from one another. Un... | Wikipedia - Atom - Summary | 152 | 826 | null |
Section: History of atomic theory > Dalton's law of multiple proportions. In the early 1800s, John Dalton compiled experimental data gathered by him and other scientists and discovered a pattern now known as the "law of multiple proportions". He noticed that in any group of chemical compounds which all contain two part... | Wikipedia - Atom - History of atomic theory > Dalton's law of multiple proportions | 334 | 1,450 | null |
There is one type of iron oxide that is a black powder which is 78.1% iron and 21.9% oxygen; and there is another iron oxide that is a red powder which is 70.4% iron and 29.6% oxygen. Adjusting these figures, in the black powder there is about 28 g of oxygen for every 100 g of iron, and in the red powder there is about... | Wikipedia - Atom - History of atomic theory > Dalton's law of multiple proportions | 343 | 1,319 | null |
Section: History of atomic theory > Discovery of the electron. In 1897, J. J. Thomson discovered that cathode rays can be deflected by electric and magnetic fields, which meant that cathode rays are not a form of light but made of electrically charged particles, and their charge was negative given the direction the par... | Wikipedia - Atom - History of atomic theory > Discovery of the electron | 224 | 1,168 | null |
Section: History of atomic theory > Discovery of the nucleus. The electrons in the atom logically had to be balanced out by a commensurate amount of positive charge, but Thomson had no idea where this positive charge came from, so he tentatively proposed that it was everywhere in the atom, the atom being in the shape o... | Wikipedia - Atom - History of atomic theory > Discovery of the nucleus | 332 | 1,722 | null |
Section: History of atomic theory > Bohr model. A problem in classical mechanics is that an accelerating charged particle radiates electromagnetic radiation, causing the particle to lose kinetic energy. Circular motion counts as acceleration, which means that an electron orbiting a central charge should spiral down int... | Wikipedia - Atom - History of atomic theory > Bohr model | 171 | 909 | null |
Section: History of atomic theory > Discovery of protons and neutrons. Back in 1815, William Prout observed that the atomic weights of many elements were multiples of hydrogen's atomic weight, which is in fact true for all of them if one takes isotopes into account. In 1898, J. J. Thomson found that the positive charge... | Wikipedia - Atom - History of atomic theory > Discovery of protons and neutrons | 325 | 1,634 | null |
The atomic weight of each element is higher than its proton number, so Rutherford hypothesized that the surplus weight was carried by unknown particles with no electric charge and a mass equal to that of the proton. In 1928, Walter Bothe observed that beryllium emitted a highly penetrating, electrically neutral radiati... | Wikipedia - Atom - History of atomic theory > Discovery of protons and neutrons | 233 | 1,207 | null |
Section: History of atomic theory > The current consensus model. In 1925, Werner Heisenberg published the first consistent mathematical formulation of quantum mechanics (matrix mechanics). One year earlier, Louis de Broglie had proposed that all particles behave like waves to some extent, and in 1926 Erwin Schrödinger ... | Wikipedia - Atom - History of atomic theory > The current consensus model | 232 | 1,231 | null |
Section: Structure > Subatomic particles. Though the word atom originally denoted a particle that cannot be cut into smaller particles, in modern scientific usage the atom is composed of various subatomic particles. The constituent particles of an atom are the electron, the proton, and the neutron. The electron is the ... | Wikipedia - Atom - Structure > Subatomic particles | 327 | 1,601 | null |
Neutrons are the heaviest of the three constituent particles, but their mass can be reduced by the nuclear binding energy. Neutrons and protons (collectively known as nucleons) have comparable dimensions—on the order of 2.5×10−15 m—although the 'surface' of these particles is not sharply defined. The neutron was discov... | Wikipedia - Atom - Structure > Subatomic particles | 302 | 1,360 | null |
Section: Structure > Nucleus. All the bound protons and neutrons in an atom make up a tiny atomic nucleus, and are collectively called nucleons. The radius of a nucleus is approximately equal to 1.07 A 3 {\displaystyle 1.07{\sqrt[{3}]{A}}} femtometres, where A {\displaystyle A} is the total number of nucleons. This is ... | Wikipedia - Atom - Structure > Nucleus | 326 | 1,466 | null |
Thus, every proton in the nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and to all electrons of the electron cloud. A nucleus that has a different number of protons than neutrons can potentially drop to a lower energy state through a radioactiv... | Wikipedia - Atom - Structure > Nucleus | 284 | 1,442 | null |
If this modifies the number of protons in a nucleus, the atom changes to a different chemical element. If the mass of the nucleus following a fusion reaction is less than the sum of the masses of the separate particles, then the difference between these two values can be emitted as a type of usable energy (such as a ga... | Wikipedia - Atom - Structure > Nucleus | 295 | 1,418 | null |
Section: Structure > Electron cloud. The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed for the electron to escap... | Wikipedia - Atom - Structure > Electron cloud | 327 | 1,765 | null |
These characteristic energy values, defined by the differences in the energies of the quantum states, are responsible for atomic spectral lines. The amount of energy needed to remove or add an electron—the electron binding energy—is far less than the binding energy of nucleons. For example, it requires only 13.6 eV to ... | Wikipedia - Atom - Structure > Electron cloud | 166 | 844 | null |
Section: Properties > Nuclear properties. By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly... | Wikipedia - Atom - Properties > Nuclear properties | 313 | 1,420 | null |
This collection of 286 nuclides are known as primordial nuclides. Finally, an additional 53 short-lived nuclides are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium), or as products of natural energetic processes on Earth, such as cosmic ray bombardment (for examp... | Wikipedia - Atom - Properties > Nuclear properties | 315 | 1,358 | null |
Of the 251 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: hydrogen-2 (deuterium), lithium-6, boron-10, and nitrogen-14. (Tantalum-180m is odd-odd and observationally stable, but is predicted to decay with a very long half-life.) Also, only four naturally occurring, radio... | Wikipedia - Atom - Properties > Nuclear properties | 162 | 623 | null |
Section: Properties > Mass. The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses ... | Wikipedia - Atom - Properties > Mass | 345 | 1,387 | null |
Section: Properties > Shape and size. Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. This assumes the atom to exhibit a spherical shape, which is only obeyed for... | Wikipedia - Atom - Properties > Shape and size | 334 | 1,677 | null |
Atomic dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they cannot be viewed using an optical microscope, although individual atoms can be observed using a scanning tunneling microscope. To visualize the minuteness of the atom, consider that a typical human hair is about 1 millio... | Wikipedia - Atom - Properties > Shape and size | 153 | 698 | null |
Section: Properties > Radioactive decay. Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force,... | Wikipedia - Atom - Properties > Radioactive decay | 348 | 1,743 | null |
The excited state of a nucleus which results in gamma emission usually occurs following the emission of an alpha or a beta particle. Thus, gamma decay usually follows alpha or beta decay. Other more rare types of radioactive decay include ejection of neutrons or protons or clusters of nucleons from a nucleus, or more t... | Wikipedia - Atom - Properties > Radioactive decay | 222 | 1,117 | null |
Section: Properties > Magnetic moment. Elementary particles possess an intrinsic quantum mechanical property known as spin. This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be... | Wikipedia - Atom - Properties > Magnetic moment | 330 | 1,666 | null |
The orbitals of neighboring atoms overlap and a lower energy state is achieved when the spins of unpaired electrons are aligned with each other, a spontaneous process known as an exchange interaction. When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field.... | Wikipedia - Atom - Properties > Magnetic moment | 208 | 1,054 | null |
Section: Properties > Energy levels. The potential energy of an electron in an atom is negative relative to when the distance from the nucleus goes to infinity; its dependence on the electron's position reaches the minimum inside the nucleus, roughly in inverse proportion to the distance. In the quantum-mechanical mode... | Wikipedia - Atom - Properties > Energy levels | 345 | 1,751 | null |
The energy of an emitted photon is proportional to its frequency, so these specific energy levels appear as distinct bands in the electromagnetic spectrum. Each element has a characteristic spectrum that can depend on the nuclear charge, subshells filled by electrons, the electromagnetic interactions between the electr... | Wikipedia - Atom - Properties > Energy levels | 341 | 1,891 | null |
The interaction of the magnetic field with the atom shifts these electron configurations to slightly different energy levels, resulting in multiple spectral lines. The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenom... | Wikipedia - Atom - Properties > Energy levels | 169 | 937 | null |
Section: Properties > Valence and bonding behavior. Valency is the combining power of an element. It is determined by the number of bonds it can form to other atoms or groups. The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in that shell are called valenc... | Wikipedia - Atom - Properties > Valence and bonding behavior | 313 | 1,622 | null |
Section: Properties > States. Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. By varying the conditions, materials can transition between solids, liquids, gases, and plasmas. Within a state, a material can also exist in different allo... | Wikipedia - Atom - Properties > States | 169 | 827 | null |
Section: Identification. While atoms are too small to be seen, devices such as the scanning tunneling microscope (STM) enable their visualization at the surfaces of solids. The microscope uses the quantum tunneling phenomenon, which allows particles to pass through a barrier that would be insurmountable in the classica... | Wikipedia - Atom - Identification | 341 | 1,750 | null |
If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope in the sample by measuring the intensity of the different beams of ions. Techniques to vaporize atoms include inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometr... | Wikipedia - Atom - Identification | 292 | 1,473 | null |
Section: Origin and current state. Baryonic matter forms about 4% of the total energy density of the observable universe, with an average density of about 0.25 particles/m3 (mostly protons and electrons). Within a galaxy such as the Milky Way, particles have a much higher concentration, with the density of matter in th... | Wikipedia - Atom - Origin and current state | 246 | 1,149 | null |
Section: Origin and current state > Formation. Electrons are thought to exist in the Universe since early stages of the Big Bang. Atomic nuclei forms in nucleosynthesis reactions. In about three minutes Big Bang nucleosynthesis produced most of the helium, lithium, and deuterium in the Universe, and perhaps some of the... | Wikipedia - Atom - Origin and current state > Formation | 318 | 1,558 | null |
Section: Origin and current state > Earth. Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine ... | Wikipedia - Atom - Origin and current state > Earth | 330 | 1,593 | null |
Section: Origin and current state > Rare and theoretical forms > Superheavy elements. All nuclides with atomic numbers higher than 82 (lead) are known to be radioactive. No nuclide with an atomic number exceeding 92 (uranium) exists on Earth as a primordial nuclide, and heavier elements generally have shorter half-live... | Wikipedia - Atom - Origin and current state > Rare and theoretical forms > Superheavy elements | 174 | 807 | null |
Section: Origin and current state > Rare and theoretical forms > Exotic matter. Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. When a matter an... | Wikipedia - Atom - Origin and current state > Rare and theoretical forms > Exotic matter | 236 | 1,139 | null |
Article: Biliprotein. Biliproteins are pigment protein compounds that are located in photosynthesising organisms such as algae, and sometimes also in certain insects. They refer to any protein that contains a bilin chromophore. In plants and algae, the main function of biliproteins is to make the process of light accum... | Wikipedia - Biliprotein - Summary | 307 | 1,422 | null |
Section: Functions > In plants and algae. Biliproteins found in plants and algae serve as a system of pigments whose purpose is to detect and absorb light needed for photosynthesis. The absorption spectra of biliproteins complements that of other photosynthetic pigments such as chlorophyll or carotene. The pigments det... | Wikipedia - Biliprotein - Functions > In plants and algae | 222 | 883 | null |
Section: Structure. The structure of biliproteins is typically characterised by bilin chromophores arranged in linear tetrapyrrolic formation, and the bilins are covalently bound to apoproteins via thioether bonds. Each type of biliprotein has a unique bilin that belongs to it (e.g. phycoerythrobilin is the chromophore... | Wikipedia - Biliprotein - Structure | 301 | 1,132 | null |
Section: Classes of biliproteins > Phycobiliproteins. Phycobiliproteins are found in cyanobacteria (also known as blue-green algae) and algae groups such as rhodophyta (red algae) and cryptophytes. Major phycobiliproteins include variations of phycocyanin (blue-pigment), variations of phycoerythrin (red pigment), and a... | Wikipedia - Biliprotein - Classes of biliproteins > Phycobiliproteins | 251 | 926 | null |
Section: Classes of biliproteins > Phycobiliproteins > Phycochromes. Phycochromes are a subclass of phycobiliprotein that was initially recognised only as light sensory pigments in cyanobacteria. They are now deemed to constitute of all possible photoreversibly photochromic pigments, regardless of function. They are al... | Wikipedia - Biliprotein - Classes of biliproteins > Phycobiliproteins > Phycochromes | 278 | 1,033 | null |
Section: Classes of biliproteins > Phytochromes. Phytochromes (also known as phys) were initially discovered in green plants in 1945. The photoreversible pigment was later found in fungi, mosses, and other algae groups due to the development of whole-genome sequencing, as explained in Peter H. Quail's 2010 journal arti... | Wikipedia - Biliprotein - Classes of biliproteins > Phytochromes | 253 | 1,127 | null |
Section: Classes of biliproteins > Lipocalins (Insect biliproteins). The lipocalins that have been identified as biliproteins have been found in a wide variety of insects, but mainly in the order Lepidoptera. Scientists have discovered them in the large white butterfly and a number of moth and silkmoth species, includi... | Wikipedia - Biliprotein - Classes of biliproteins > Lipocalins (Insect biliproteins) | 225 | 907 | null |
Section: Comparison of biliproteins from different organisms. In a 1988 study conducted by Hugo Scheer and Harmut Kayser, biliproteins were extracted from the large white butterfly and puss moth and their respective properties were examined. Their properties were compared to those of plant and algae biliproteins, and t... | Wikipedia - Biliprotein - Comparison of biliproteins from different organisms | 343 | 1,493 | null |
Section: Applications > Bioimaging. Fluorescent proteins have had a substantial impact on bioimaging, which is why biliproteins have made suitable candidates for the application, due to their properties of fluorescence, light-harvesting, light-sensitivity and photoswitching (the latter occurring only in phytochromes). ... | Wikipedia - Biliprotein - Applications > Bioimaging | 233 | 1,027 | null |
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