ETYM New Lat., from Greek litheios of stone, from lithos stone.
Soft, ductile, silver-white, metallic element, symbol Li, atomic number 3, atomic weight 6.941. It is one of the alkali metals, has a very low density (far less than most woods), and floats on water (specific gravity 0.57); it is the lightest of all metals. Lithium is used to harden alloys, and in batteries; its compounds are used in medicine to treat manic depression.
Lithium was named in 1818 by Swedish chemist Jöns Berzelius, having been discovered the previous year by his student Johan A Arfwedson (1792–1841). Berzelius named it after “stone” because it is found in most igneous rocks and many mineral springs.
A soft silver-white univalent element of the alkali metal group; the lightest metal known; occurs in several minerals; SYN. Li, atomic number 3.