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Lithium
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Lithium is the lightest metal and has a density that is only half that of water. Like all alkali metals, Lithium reacts easily in water and doesn't occur freely in nature due to its activity, nevertheless it is still less reactive than the chemically similar sodium. When placed over a flame, this metal gives off a striking crimson color but when it burns strongly, the flame becomes a brilliant white. This is also an univalent element.
Because of its large specific heat (the largest of any solid), lithium is used in heat transfer applications. It is also an important battery anode material due to its high electrochemical potential. Other uses:
Lithium (Greek lithos, meaning "stone") was discovered by Johann Arfvedson in 1817. Arfvedson found the new element within the minerals spodumene and lepidolite in a petalite ore, LiAl(Si2O5)2, he was analyzing from the island Utö[?] in Sweden. In 1818 C.G. Gmelin[?] was the first to observe that lithium salts give a bright red color in flame. Both men tried and failed to isolate the element from its salts, however.
The element was not isolated until W.T. Brande[?] and Sir Humphrey Davy later used electrolysis on lithium oxide[?]. Commercial production of lithium metal was achieved in 1923 by the German company Metallgesellschaft AG[?] through using electrolysis of molten lithium chloride[?] and potassium chloride.
It was apparently given the name "lithium" because it was discovered from a mineral while other common alkali metals were first discovered from plant tissue.
Lithium is widely distributed but doesn't occur in nature in its free form; due to its reactivity, it is always found bound with one or more other elements or compounds. It forms a minor part of almost all igneous rocks and is also found in many natural brines.
Since the end of World War II, lithium production has greatly increased. The metal is separated from other elements in igneous rocks, and is also extracted from the the water of mineral springs[?]. Lepidolite, spodumene, petalite, and amblygonite are the more important minerals containing it.
In the United States lithium is recovered from brine pools in the dry Searles Lake[?], in California, and from places in Nevada and elsewhere. The metal, which is silvery in appearance like sodium, potassium and other members of the alkali metal series, is produced electrolytically from a mixture of fused lithium and potassium chloride. This metal cost about US$ 300 per pound in 1997.
Isolation (* follow):
cathode: Li+* + e- --> Li* anode: Cl-* --> ½Cl2 (gas) + e-
Naturally occurring lithium is composed of 2 stable isotopes Li-6 and Li-7 with Li-7 being the most abundant (92.5% natural abundance). Six radioisotopes have been characterized with the most stable being Li-8 with a half-life of 838 ms and Li-9 with a half-life of 178.3 ms. All of the remaining radioactive isotopes have half-lifes that are less than 8.5 ms or are not known.
The isotopes of lithium range in atomic weight from 4.027 amu (Li-4) to 11.0438 amu (Li-11). The primary decay mode before the most abundant stable isotope, Li-7, is proton emission[?] (with one case of alpha decay) and the primary mode after is beta emission (with some neutron emission[?]). The primary decay products before Li-7 are element 2 (helium) isotopes and the primary products after are element 4 (beryllium) isotopes.
Lithium-7 is one of the primordial elements (produced in big bang nucleosysthesis[?]). Lithium isotopes fractionate substantially during a wide variety of natural processes, including mineral formation[?] (chemical precipitation), metabolism, ion exchange[?] (Li substitutes for magnesium and iron in octahedral sites in clay minerals, where Li-6 is preferential over Li-7), hyperfiltration, and rock alteration.
Like the other alkali metals, lithium in its pure form is highly flammable and slightly explosive when exposed to air and especially water. This metal is also corrosive and requires special handling to avoid skin contact. When it is stored it should be placed in an inflammable liquid hydrocarbon such as naphtha. Lithium plays no natural biological role and is considered to be slightly toxic.
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