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doc20663 | Due to the great rarity of odd–odd nuclei, almost all the primordial isotopes of the alkali metals are odd–even (the exceptions being the light stable isotope lithium-6 and the long-lived radioisotope potassium-40). For a given odd mass number, there can be only a single beta-stable nuclide, since there is not a differ... | Alkali metal |
doc20664 | All of the alkali metals except lithium and caesium have at least one naturally occurring radioisotope: sodium-22 and sodium-24 are trace radioisotopes produced cosmogenically,[38] potassium-40 and rubidium-87 have very long half-lives and thus occur naturally,[39] and all isotopes of francium are radioactive.[39] Caes... | Alkali metal |
doc20665 | Caesium-137, with a half-life of 30.17 years, is one of the two principal medium-lived fission products, along with strontium-90, which are responsible for most of the radioactivity of spent nuclear fuel after several years of cooling, up to several hundred years after use. It constitutes most of the radioactivity stil... | Alkali metal |
doc20666 | The alkali metals are more similar to each other than the elements in any other group are to each other.[5] For instance, when moving down the table, all known alkali metals show increasing atomic radius,[16] decreasing electronegativity,[16] increasing reactivity,[5] and decreasing melting and boiling points[16] as we... | Alkali metal |
doc20667 | The atomic radii of the alkali metals increase going down the group.[16] Because of the shielding effect, when an atom has more than one electron shell, each electron feels electric repulsion from the other electrons as well as electric attraction from the nucleus.[49] In the alkali metals, the outermost electron only ... | Alkali metal |
doc20668 | The ionic radii of the alkali metals are much smaller than their atomic radii. This is because the outermost electron of the alkali metals is in a different electron shell than the inner electrons, and thus when it is removed the resulting atom has one fewer electron shell and is smaller. Additionally, the effective nu... | Alkali metal |
doc20669 | The first ionisation energy of an element or molecule is the energy required to move the most loosely held electron from one mole of gaseous atoms of the element or molecules to form one mole of gaseous ions with electric charge +1. The factors affecting the first ionisation energy are the nuclear charge, the amount of... | Alkali metal |
doc20670 | The second ionisation energy of the alkali metals is much higher than the first as the second-most loosely held electron is part of a fully filled electron shell and is thus difficult to remove.[5] | Alkali metal |
doc20671 | The reactivities of the alkali metals increase going down the group. This is the result of a combination of two factors: the first ionisation energies and atomisation energies of the alkali metals. Because the first ionisation energy of the alkali metals decreases down the group, it is easier for the outermost electron... | Alkali metal |
doc20672 | Electronegativity is a chemical property that describes the tendency of an atom or a functional group to attract electrons (or electron density) towards itself.[51] If the bond between sodium and chlorine in sodium chloride were covalent, the pair of shared electrons would be attracted to the chlorine because the effec... | Alkali metal |
doc20673 | Because of the higher electronegativity of lithium, some of its compounds have a more covalent character. For example, lithium iodide (LiI) will dissolve in organic solvents, a property of most covalent compounds.[16] Lithium fluoride (LiF) is the only alkali halide that is not soluble in water,[5] and lithium hydroxid... | Alkali metal |
doc20674 | The melting point of a substance is the point where it changes state from solid to liquid while the boiling point of a substance (in liquid state) is the point where the vapour pressure of the liquid equals the environmental pressure surrounding the liquid[52][53] and all the liquid changes state to gas. As a metal is ... | Alkali metal |
doc20675 | The alkali metals all have the same crystal structure (body-centred cubic)[6] and thus the only relevant factors are the number of atoms that can fit into a certain volume and the mass of one of the atoms, since density is defined as mass per unit volume. The first factor depends on the volume of the atom and thus the ... | Alkali metal |
doc20676 | The alkali metals form complete series of compounds with all usually encountered anions, which well illustrate group trends. These compounds can be described as involving the alkali metals losing electrons to acceptor species and forming monopositive ions.[6]:79 This description is most accurate for alkali halides and ... | Alkali metal |
doc20677 | All the alkali metals react vigorously or explosively with cold water, producing an aqueous solution of a strongly basic alkali metal hydroxide and releasing hydrogen gas.[50] This reaction becomes more vigorous going down the group: lithium reacts steadily with effervescence, but sodium and potassium can ignite and ru... | Alkali metal |
doc20678 | Recent research has suggested that the explosive behavior of alkali metals in water is driven by a Coulomb explosion rather than solely by rapid generation of hydrogen itself.[55] All alkali metals melt as a part of the reaction with water. Water molecules ionise the bare metallic surface of the liquid metal, leaving a... | Alkali metal |
doc20679 | The hydroxides themselves are the most basic hydroxides known, reacting with acids to give salts and with alcohols to give oligomeric alkoxides. They easily react with carbon dioxide to form carbonates or bicarbonates, or with hydrogen sulfide to form sulfides or bisulfides, and may be used to separate thiols from petr... | Alkali metal |
doc20680 | The alkali metals form many intermetallic compounds with each other and the elements from groups 2 to 13 in the periodic table of varying stoichiometries,[6]:81 such as the sodium amalgams with mercury, including Na5Hg8 and Na3Hg.[56] Some of these have ionic characteristics: taking the alloys with gold, the most elect... | Alkali metal |
doc20681 | The intermetallic compounds of the alkali metals with the heavier group 13 elements (aluminium, gallium, indium, and thallium), such as NaTl, are poor conductors or semiconductors, unlike the normal alloys with the preceding elements, implying that the alkali metal involved has lost an electron to the Zintl anions invo... | Alkali metal |
doc20682 | Boron is a special case, being the only nonmetal in group 13. The alkali metal borides tend to be boron-rich, involving appreciable boron–boron bonding involving deltahedral structures,[6]:147–8 and are thermally unstable due to the alkali metals having a very high vapour pressure at elevated temperatures. This makes d... | Alkali metal |
doc20683 | Lithium and sodium react with carbon to form acetylides, Li2C2 and Na2C2, which can also be obtained by reaction of the metal with acetylene. Potassium, rubidium, and caesium react with graphite; their atoms are intercalated between the hexagonal graphite layers, forming graphite intercalation compounds of formulae MC6... | Alkali metal |
doc20684 | When the alkali metals react with the heavier elements in the carbon group (silicon, germanium, tin, and lead), ionic substances with cage-like structures are formed, such as the silicides M4Si4 (M = K, Rb, or Cs), which contains M+ and tetrahedral Si4−
4 ions.[8] The chemistry of alkali metal germanides, involving the... | Alkali metal |
doc20685 | Lithium, the lightest of the alkali metals, is the only alkali metal which reacts with nitrogen at standard conditions, and its nitride is the only stable alkali metal nitride. Nitrogen is an unreactive gas because breaking the strong triple bond in the dinitrogen molecule (N2) requires a lot of energy. The formation o... | Alkali metal |
doc20686 | All the alkali metals react readily with phosphorus and arsenic to form phosphides and arsenides with the formula M3Pn (where M represents an alkali metal and Pn represents a pnictogen – phosphorus, arsenic, antimony, or bismuth). This is due to the greater size of the P3− and As3− ions, so that less lattice energy nee... | Alkali metal |
doc20687 | All the alkali metals react vigorously with oxygen at standard conditions. They form various types of oxides, such as simple oxides (containing the O2− ion), peroxides (containing the O2−
2 ion, where there is a single bond between the two oxygen atoms), superoxides (containing the O−
2 ion), and many others. Lithium b... | Alkali metal |
doc20688 | The smaller alkali metals tend to polarise the larger anions (the peroxide and superoxide) due to their small size. This attracts the electrons in the more complex anions towards one of its constituent oxygen atoms, forming an oxide ion and an oxygen atom. This causes lithium to form the oxide exclusively on reaction w... | Alkali metal |
doc20689 | Rubidium and caesium can form a great variety of suboxides with the metals in formal oxidation states below +1.[6]:85 Rubidium can form Rb6O and Rb9O2 (copper-coloured) upon oxidation in air, while caesium forms an immense variety of oxides, such as the ozonide CsO3[76][77] and several brightly coloured suboxides,[78] ... | Alkali metal |
doc20690 | The alkali metals can also react analogously with the heavier chalcogens (sulfur, selenium, tellurium, and polonium), and all the alkali metal chalcogenides are known (with the exception of francium's). Reaction with an excess of the chalcogen can similarly result in lower chalcogenides, with chalcogen ions containing ... | Alkali metal |
doc20691 | The alkali metals are among the most electropositive elements on the periodic table and thus tend to bond ionically to the most electronegative elements on the periodic table, the halogens (fluorine, chlorine, bromine, iodine, and astatine), forming salts known as the alkali metal halides. The reaction is very vigorous... | Alkali metal |
doc20692 | The alkali metals also react similarly with hydrogen to form ionic alkali metal hydrides, where the hydride anion acts as a pseudohalide: these are often used as reducing agents, producing hydrides, complex metal hydrides, or hydrogen gas.[6]:83[8] Other pseudohalides are also known, notably the cyanides. These are iso... | Alkali metal |
doc20693 | Alkali metal cations do not usually form coordination complexes with simple Lewis bases due to their low charge of just +1 and their relatively large size; thus the Li+ ion forms most complexes and the heavier alkali metal ions form less and less (though exceptions occur for weak complexes).[6]:90 Lithium in particular... | Alkali metal |
doc20694 | The alkali metals dissolve slowly in liquid ammonia, forming ammoniacal solutions of solvated M+ and e−, which react to form hydrogen gas and the alkali metal amide (MNH2, where M represents an alkali metal): this was first noted by Humphry Davy in 1809 and rediscovered by W. Weyl in 1864. The process may be speeded up... | Alkali metal |
doc20695 | Being the smallest alkali metal, lithium forms the widest variety of and most stable organometallic compounds, which are bonded covalently. Organolithium compounds are electrically non-conducting volatile solids or liquids that melt at low temperatures, and tend to form oligomers with the structure (RLi)x where R is th... | Alkali metal |
doc20696 | Alkyllithiums and aryllithiums may also react with N,N-disubstituted amides to give aldehydes and ketones, and symmetrical ketones by reacting with carbon monoxide. They thermally decompose to eliminate a β-hydrogen, producing alkenes and lithium hydride: another route is the reaction of ethers with alkyl- and aryllit... | Alkali metal |
doc20697 | Unlike the organolithium compounds, the organometallic compounds of the heavier alkali metals are predominantly ionic. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are commercially available and exhibit more convenient reactivity. The p... | Alkali metal |
doc20698 | Alkyl and aryl derivatives of sodium and potassium tend to react with air. They cause the cleavage of ethers, generating alkoxides. Unlike alkyllithium compounds, alkylsodiums and alkylpotassiums cannot be made by reacting the metals with alkyl halides because Wurtz coupling occurs:[73]:265 | Alkali metal |
doc20699 | As such, they have to be made by reacting alkylmercury compounds with sodium or potassium metal in inert hydrocarbon solvents. While methylsodium forms tetramers like methyllithium, methylpotassium is more ionic and has the nickel arsenide structure with discrete methyl anions and potassium cations.[73]:265 | Alkali metal |
doc20700 | The alkali metals and their hydrides react with acidic hydrocarbons, for example cyclopentadienes and terminal alkynes, to give salts. Liquid ammonia, ether, or hydrocarbon solvents are used, the most common of which being tetrahydrofuran. The most important of these compounds is sodium cyclopentadienide, NaC5H5, an im... | Alkali metal |
doc20701 | Although francium is the heaviest alkali metal that has been discovered, there has been some theoretical work predicting the physical and chemical characteristics of the hypothetical heavier alkali metals. Being the first period 8 element, the undiscovered element ununennium (element 119) is predicted to be the next al... | Alkali metal |
doc20702 | The stabilisation of ununennium's valence electron and thus the contraction of the 8s orbital cause its atomic radius to be lowered to 240 pm,[33]:1729–1730 very close to that of rubidium (247 pm),[5] so that the chemistry of ununennium in the +1 oxidation state should be more similar to the chemistry of rubidium than ... | Alkali metal |
doc20703 | Not as much work has been done predicting the properties of the alkali metals beyond ununennium. Although a simple extrapolation of the periodic table would put element 169, unhexennium, under ununennium, Dirac-Fock calculations predict that the next alkali metal after ununennium may actually be element 165, unhexpenti... | Alkali metal |
doc20704 | The probable properties of further alkali metals beyond unhexpentium have not been explored yet as of 2015; in fact, it is suspected that they may not be able to exist.[95] In periods 8 and above of the periodic table, relativistic and shell-structure effects become so strong that extrapolations from lighter congeners ... | Alkali metal |
doc20705 | Many other substances are similar to the alkali metals in their tendency to form monopositive cations. Analogously to the pseudohalogens, they have sometimes been called "pseudo-alkali metals". These substances include some elements and many more polyatomic ions; the polyatomic ions are especially similar to the alkali... | Alkali metal |
doc20706 | The element hydrogen, with one electron per neutral atom, is usually placed at the top of Group 1 of the periodic table for convenience, but hydrogen is not normally considered to be an alkali metal;[103] when it is considered to be an alkali metal, it is because of its atomic properties and not its chemical properties... | Alkali metal |
doc20707 | Hydrogen, like the alkali metals, has one valence electron[73] and reacts easily with the halogens,[73] but the similarities end there because of the small size of a bare proton H+ compared to the alkali metal cations.[73] Its placement above lithium is primarily due to its electron configuration.[103][107] It is somet... | Alkali metal |
doc20708 | The first ionisation energy of hydrogen (1312.0 kJ/mol) is much higher than that of the alkali metals.[109][110] As only one additional electron is required to fill in the outermost shell of the hydrogen atom, hydrogen often behaves like a halogen, forming the negative hydride ion, and is very occasionally considered t... | Alkali metal |
doc20709 | The 1s1 electron configuration of hydrogen, while superficially similar to that of the alkali metals (ns1), is unique because there is no 1p subshell. Hence it can lose an electron to form the hydron H+, or gain one to form the hydride ion H−.[6]:43 In the former case it resembles superficially the alkali metals; in th... | Alkali metal |
doc20710 | The ammonium ion (NH+
4) has very similar properties to the heavier alkali metals, acting as an alkali metal intermediate between potassium and rubidium,[102][114] and is often considered a close relative.[115][116][117] For example, most alkali metal salts are soluble in water, a property which ammonium salts share.[1... | Alkali metal |
doc20711 | Other "pseudo-alkali metals" include the alkylammonium cations, in which some of the hydrogen atoms in the ammonium cation are replaced by alkyl or aryl groups. In particular, the quaternary ammonium cations (NR+
4) are very useful since they are permanently charged, and they are often used as an alternative to the exp... | Alkali metal |
doc20712 | Cobaltocene, Co(C5H5)2, is a metallocene, the cobalt analogue of ferrocene. It is a dark purple solid. Cobaltocene has 19 valence electrons, one more than usually found in organotransition metal complexes, such as its very stable relative, ferrocene, in accordance with the 18-electron rule. This additional electron occ... | Alkali metal |
doc20713 | Thallium is the heaviest stable element in group 13 of the periodic table. At the bottom of the periodic table, the inert pair effect is quite strong, because of the relativistic stabilisation of the 6s orbital and the decreasing bond energy as the atoms increase in size so that the amount of energy released in forming... | Alkali metal |
doc20714 | The group 11 metals (or coinage metals), copper, silver, and gold, are typically categorised as transition metals given they can form ions with incomplete d-shells. Physically, they have the relatively low melting points and high electronegativity values associated with post-transition metals. "The filled d subshell an... | Alkali metal |
doc20715 | In Mendeleev's 1871 periodic table, copper, silver, and gold are listed twice, once under group VIII (with the iron triad and platinum group metals), and once under group IB. Group IB was nonetheless parenthesised to note that it was tentative. Mendeleev's main criterion for group assignment was the maximum oxidation s... | Alkali metal |
doc20716 | The coinage metals were traditionally regarded as a subdivision of the alkali metal group, due to them sharing the characteristic s1 electron configuration of the alkali metals (group 1: p6s1; group 11: d10s1). However, the similarities are largely confined to the stoichiometries of the +1 compounds of both groups, and... | Alkali metal |
doc20717 | Sodium compounds have been known since ancient times; salt (sodium chloride) has been an important commodity in human activities, as testified by the English word salary, referring to salarium, money paid to Roman soldiers for the purchase of salt.[132] While potash has been used since ancient times, it was not underst... | Alkali metal |
doc20718 | Pure potassium was first isolated in 1807 in England by Sir Humphry Davy, who derived it from caustic potash (KOH, potassium hydroxide) by the use of electrolysis of the molten salt with the newly invented voltaic pile. Previous attempts at electrolysis of the aqueous salt were unsuccessful due to potassium's extreme r... | Alkali metal |
doc20719 | Petalite (LiAlSi4O10) was discovered in 1800 by the Brazilian chemist José Bonifácio de Andrada in a mine on the island of Utö, Sweden.[140][141][142] However, it was not until 1817 that Johan August Arfwedson, then working in the laboratory of the chemist Jöns Jacob Berzelius, detected the presence of a new element wh... | Alkali metal |
doc20720 | Rubidium and caesium were the first elements to be discovered using the spectroscope, invented in 1859 by Robert Bunsen and Gustav Kirchhoff.[146] The next year, they discovered caesium in the mineral water from Bad Dürkheim, Germany. Their discovery of rubidium came the following year in Heidelberg, Germany, finding i... | Alkali metal |
doc20721 | Around 1865 John Newlands produced a series of papers where he listed the elements in order of increasing atomic weight and similar physical and chemical properties that recurred at intervals of eight; he likened such periodicity to the octaves of music, where notes an octave apart have similar musical functions.[150][... | Alkali metal |
doc20722 | After 1869, Dmitri Mendeleev proposed his periodic table placing lithium at the top of a group with sodium, potassium, rubidium, caesium, and thallium.[152] Two years later, Mendeleev revised his table, placing hydrogen in group 1 above lithium, and also moving thallium to the boron group. In this 1871 version, copper,... | Alkali metal |
doc20723 | There were at least four erroneous and incomplete discoveries[43][44][154][155] before Marguerite Perey of the Curie Institute in Paris, France discovered francium in 1939 by purifying a sample of actinium-227, which had been reported to have a decay energy of 220 keV. However, Perey noticed decay particles with an ene... | Alkali metal |
doc20724 | The next element below francium (eka-francium) in the periodic table would be ununennium (Uue), element 119.[33]:1729–1730 The synthesis of ununennium was first attempted in 1985 by bombarding a target of einsteinium-254 with calcium-48 ions at the superHILAC accelerator at Berkeley, California. No atoms were identif... | Alkali metal |
doc20725 | It is highly unlikely[158] that this reaction will be able to create any atoms of ununennium in the near future, given the extremely difficult task of making sufficient amounts of einsteinium-254, which is favoured for production of ultraheavy elements because of its large mass, relatively long half-life of 270 days, a... | Alkali metal |
doc20726 | The Oddo–Harkins rule holds that elements with even atomic numbers are more common that those with odd atomic numbers, with the exception of hydrogen. This rule argues that elements with odd atomic numbers have one unpaired proton and are more likely to capture another, thus increasing their atomic number. In elements ... | Alkali metal |
doc20727 | The Earth formed from the same cloud of matter that formed the Sun, but the planets acquired different compositions during the formation and evolution of the solar system. In turn, the natural history of the Earth caused parts of this planet to have differing concentrations of the elements. The mass of the Earth is app... | Alkali metal |
doc20728 | The alkali metals, due to their high reactivity, do not occur naturally in pure form in nature. They are lithophiles and therefore remain close to the Earth's surface because they combine readily with oxygen and so associate strongly with silica, forming relatively low-density minerals that do not sink down into the Ea... | Alkali metal |
doc20729 | Sodium and potassium are very abundant in earth, both being among the ten most common elements in Earth's crust;[169][170] sodium makes up approximately 2.6% of the Earth's crust measured by weight, making it the sixth most abundant element overall[171] and the most abundant alkali metal. Potassium makes up approximate... | Alkali metal |
doc20730 | Despite its chemical similarity, lithium typically does not occur together with sodium or potassium due to its smaller size.[6]:69 Due to its relatively low reactivity, it can be found in seawater in large amounts; it is estimated that seawater is approximately 0.14 to 0.25 parts per million (ppm)[172][173] or 25 micro... | Alkali metal |
doc20731 | Rubidium is approximately as abundant as zinc and more abundant than copper. It occurs naturally in the minerals leucite, pollucite, carnallite, zinnwaldite, and lepidolite,[175] although none of these contain only rubidium and no other alkali metals.[6]:70 Caesium is more abundant than some commonly known elements, su... | Alkali metal |
doc20732 | Francium-223, the only naturally occurring isotope of francium,[10][11] is the product of the alpha decay of actinium-227 and can be found in trace amounts in uranium minerals.[176] In a given sample of uranium, there is estimated to be only one francium atom for every 1018 uranium atoms.[177][178] It has been calculat... | Alkali metal |
doc20733 | The production of pure alkali metals is somewhat complicated due to their extreme reactivity with commonly used substances, such as water.[5][8] From their silicate ores, all the stable alkali metals may be obtained the same way: sulfuric acid is first used to dissolve the desired alkali metal ion and aluminium(III) io... | Alkali metal |
doc20734 | Lithium salts have to be extracted from the water of mineral springs, brine pools, and brine deposits. The metal is produced electrolytically from a mixture of fused lithium chloride and potassium chloride.[181] | Alkali metal |
doc20735 | Sodium occurs mostly in seawater and dried seabed,[5] but is now produced through electrolysis of sodium chloride by lowering the melting point of the substance to below 700 °C through the use of a Downs cell.[182][183] Extremely pure sodium can be produced through the thermal decomposition of sodium azide.[184] Potass... | Alkali metal |
doc20736 | Although sodium is less reactive than potassium, this process works because at such high temperatures potassium is more volatile than sodium and can easily be distilled off, so that the equilibrium shifts towards the right to produce more potassium gas and proceeds almost to completion.[6]:74 | Alkali metal |
doc20737 | For several years in the 1950s and 1960s, a by-product of the potassium production called Alkarb was a main source for rubidium. Alkarb contained 21% rubidium while the rest was potassium and a small fraction of caesium.[187] Today the largest producers of caesium, for example the Tanco Mine in Manitoba, Canada, produc... | Alkali metal |
doc20738 | As a result of its extreme rarity in nature,[179] most francium is synthesised in the nuclear reaction 197Au + 18O → 210Fr + 5 n, yielding francium-209, francium-210, and francium-211.[191] The greatest quantity of francium ever assembled to date is about 300,000 neutral atoms,[192] which were synthesised using the n... | Alkali metal |
doc20739 | Lithium, sodium, and potassium have many applications, while rubidium and caesium are very useful in academic contexts but do not have many applications yet.[6]:68 Lithium is often used in batteries, and lithium oxide can help process silica. Lithium stearate is a thickener and can be used to make lubricating greases; ... | Alkali metal |
doc20740 | Sodium compounds have many applications, the most well-known being sodium chloride as table salt. Sodium salts of fatty acids are used as soap.[195] Pure sodium metal also has many applications, including use in sodium-vapour lamps, which produce very efficient light compared to other types of lighting,[196][197] and c... | Alkali metal |
doc20741 | Potassium compounds are often used as fertilisers[6]:73[200] as potassium is an important element for plant nutrition. Potassium hydroxide is a very strong base, and is used to control the pH of various substances.[201][202] Potassium nitrate and potassium permanganate are often used as powerful oxidising agents.[6]:73... | Alkali metal |
doc20742 | Rubidium and caesium are often used in atomic clocks.[203] Caesium atomic clocks are extraordinarily accurate; if a clock had been made at the time of the dinosaurs, it would be off by less than four seconds (after 80 million years).[21] For that reason, caesium atoms are used as the definition of the second.[204] Rubi... | Alkali metal |
doc20743 | Francium has no commercial applications,[177][178][207] but because of francium's relatively simple atomic structure, among other things, it has been used in spectroscopy experiments, leading to more information regarding energy levels and the coupling constants between subatomic particles.[208] Studies on the light em... | Alkali metal |
doc20744 | Pure alkali metals are dangerously reactive with air and water and must be kept away from heat, fire, oxidising agents, acids, most organic compounds, halocarbons, plastics, and moisture. They also react with carbon dioxide and carbon tetrachloride, so that normal fire extinguishers are counterproductive when used on a... | Alkali metal |
doc20745 | Experiments are usually conducted using only small quantities of a few grams in a fume hood. Small quantities of lithium may be disposed of by reaction with cool water, but the heavier alkali metals should be dissolved in the less reactive isopropanol.[210][212] The alkali metals must be stored under mineral oil or an ... | Alkali metal |
doc20746 | The bioinorganic chemistry of the alkali metal ions has been extensively reviewed.[215] Solid state crystal structures have been determined for many complexes of alkali metal ions in small peptides, nucleic acid constituents, carbohydrates and ionophore complexes.[216] | Alkali metal |
doc20747 | Lithium naturally only occurs in traces in biological systems and has no known biological role, but does have effects on the body when ingested.[217] Lithium carbonate is used as a mood stabiliser in psychiatry to treat bipolar disorder (manic-depression) in daily doses of about 0.5 to 2Â grams, although there are side... | Alkali metal |
doc20748 | Sodium and potassium occur in all known biological systems, generally functioning as electrolytes inside and outside cells.[221][222] Sodium is an essential nutrient that regulates blood volume, blood pressure, osmotic equilibrium and pH; the minimum physiological requirement for sodium is 500 milligrams per day.[223] ... | Alkali metal |
doc20749 | Potassium is the major cation (positive ion) inside animal cells,[221] while sodium is the major cation outside animal cells.[221][222] The concentration differences of these charged particles causes a difference in electric potential between the inside and outside of cells, known as the membrane potential. The balance... | Alkali metal |
doc20750 | Due to their similar atomic radii, rubidium and caesium in the body mimic potassium and are taken up similarly. Rubidium has no known biological role, but may help stimulate metabolism,[232][233][234] and, similarly to caesium,[232][235] replace potassium in the body causing potassium deficiency.[232][234] Partial subs... | Alkali metal |
doc20751 | Caesium compounds are rarely encountered by most people, but most caesium compounds are mildly toxic. Like rubidium, caesium tends to substitute potassium in the body, but is significantly larger and is therefore a poorer substitute.[235] Excess caesium can lead to hypokalemia, arrythmia, and acute cardiac arrest,[241]... | Alkali metal |
doc20752 | Radioisotopes of caesium require special precautions: the improper handling of caesium-137 gamma ray sources can lead to release of this radioisotope and radiation injuries. Perhaps the best-known case is the Goiânia accident of 1987, in which an improperly-disposed-of radiation therapy system from an abandoned clinic ... | Alkali metal |
doc21828 | In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta ray (fast energetic electron or positron) and a neutrino are emitted from an atomic nucleus. For example, beta decay of a neutron transforms it into a proton by the emission of an electron, or conversely a proton is converted into a... | Beta decay |
doc21829 | Beta decay is a consequence of the weak force, which is characterized by relatively lengthy decay times. Nucleons are composed of up or down quarks,[2] and the weak force allows a quark to change type by the exchange of a W boson and the creation of an electron/antineutrino or positron/neutrino pair. For example, a neu... | Beta decay |
doc21830 | Electron capture is sometimes included as a type of beta decay,[3] because the basic nuclear process, mediated by the weak force, is the same. In electron capture, an inner atomic electron is captured by a proton in the nucleus, transforming it into a neutron, and an electron neutrino is released. | Beta decay |
doc21831 | The two types of beta decay are known as beta minus and beta plus. In beta minus (β−) decay, a neutron is converted to a proton and the process creates an electron and an electron antineutrino; while in beta plus (β+) decay, a proton is converted to a neutron and the process creates a positron and an electron neutrino.... | Beta decay |
doc21832 | Beta decay conserves a quantum number known as the lepton number, or the number of electrons and their associated neutrinos (other leptons are the muon and tau particles). These particles have lepton number +1, while their antiparticles have lepton number −1. Since a proton or neutron has lepton number zero, β+ decay (... | Beta decay |
doc21833 | An example of electron emission (β− decay) is the decay of carbon-14 into nitrogen-14 with a half-life of about 5,730 years: | Beta decay |
doc21834 | In this form of decay, the original element becomes a new chemical element in a process known as nuclear transmutation. This new element has an unchanged mass number A, but an atomic number Z that is increased by one. As in all nuclear decays, the decaying element (in this case 14
6C) is known as the parent nuclide whi... | Beta decay |
doc21835 | An example of positron emission is the decay of magnesium-23 into sodium-23 with a half-life of about 11.3 s: | Beta decay |
doc21836 | β+ decay also results in nuclear transmutation, with the resulting element having an atomic number that is decreased by one. | Beta decay |
doc21837 | The beta spectrum, or distribution of energy values for the beta particles, is continuous. The total energy of the decay process is divided between the electron, the antineutrino, and the recoiling nuclide. In the figure to the right, an example of an electron with 0.40 MeV energy from the beta decay of 210Bi is shown.... | Beta decay |
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