Lithium (Li) was discovered in 1817 by J.A. Arfvedson, but the free metal was not isolated until 1821, by W.T. Brande. It occurs naturally in small quantities (about 20 parts per million in the earth's crust), normally bound up with aluminum and silica in minerals. It is the smallest alkali metal, with an atomic number of 3 and an atomic weight of 6.94 amu (atomic mass unit). It has a melting point of 356.9°F (180.5°C), and a boiling point of 2,457°F (1,347°C).
Lithium carbonate is well known for its ability to calm the mood swings of manic-depressive psychosis, a serious mental disorder. Industrially, however, it is used in lubricants, in batteries, in glass (to make it harder), and in alloys of lead, aluminum, and magnesium to make them less dense and stronger.