Lithium (from Greek: Î»Î¯Î¸Î¿Ï, romanized: lithos, lit. ‘stone’) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and must be stored in mineral oil. When cut, it shows a metallic shine, but moist air rusts/wears away it quickly to a dull silvery gray, then black discolor and ruin. It never happens freely in nature, but only in (usually ionic) compounds, such as pegmatitic minerals, which were once the main source of lithium. Due to its dissolvability as an ion, it is present in ocean water and is commonly found in salt waters. Lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride.
The nucleus of the lithium atom edges on are borderline instable, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative nuclear instability, lithium is less common in the solar system than 25 of the first 32 chemical elements even though its nucleus is very light: it is an exception to the rule that heavier cell nuclei are less common. For related reasons, lithium has important uses in nuclear physics. The change of lithium atoms to helium in 1932 was the first fully man-made nuclear reaction, and lithium deuteride serves as a fusion fuel in staged thermonucleur weapons.
Lithium and its compounds have a number of industrial uses, including heat-resistant glass and ceramics, lithium grease lubricants, flux additives for iron, steel and aluminium production, lithium electrical storage devices, and lithium-ion electrical storage devices. These uses consume more than three-quarters of lithium production.
Lithium is present in organic systems in trace amounts; its functions are uncertain. Lithium salts have proven to be useful as a mood-stabilizing drug in the treatment of bi-polar disorders.