The discovery of lithium (Li) is credited to the Swedish chemist Johan August Arfwedson, who in 1817 detected the presence of an unknown element in the mineral petalite. He named the element 'lithium', from the Greek lithos meaning stone. Elemental lithium wasn't isolated until 1821, when the English chemist William Thomas Brande obtained it from the electrolysis of lithium oxide.
Lithium is the first of the alkali metals. It possesses a single valence electron that is easily lost to form a cation with a 1+ charge. This means that lithium is a good conductor of heat and electricity, and is a highly reactive element, although it is the least reactive of the alkali metals. Lithium is soft enough to be cut with a knife - when cut it has a silver colour that quickly tarnishes on exposure to air. This is due to a reaction with oxygen to form lithium oxide. Lithium is a solid at room temperature and has the highest melting and boiling points of the alkali metals. It is also the lightest metal in the periodic table and has the lowest density of all non-gaseous elements.
Lithium's low density means that it can float on water, however it also reacts with water to form hydrogen gas and lithium hydroxide. Lithium's reaction with water is less vigourous than that of the other alkali metals but is still fun to watch. Don't try this at home!
The largest use of lithium is in lithium-ion batteries (not to be confused with lithium batteries!). Lithium batteries use lithium metal as the anode and are non-rechargeable, while lithium-ion batteries use an intercalated lithium compound and can be recharged. Alloys of lithium with other metals such as magnesium and aluminium are used to make parts for aircraft. Lithium compounds are also commonly used in the treatment of bipolar disorder.
