Lithium
Lithium, symbol Li, silvery white, chemically reactive metallic element that is the lightest in weight of all metals. In group 1 (or Ia) of the periodic table (see Periodic Law ), lithium is one of the alkali metals . The atomic number of lithium is 3. Discovery of the element is generally credited to Johann A. Arfvedson in 1817. Chemically, lithium resembles sodium in its behavior. Lithium is obtained by the electrolysis of a mixture of fused lithium and potassium chloride. It tarnishes instantaneously and corrodes rapidly upon exposure to air; when it is stored it must be immersed in a liquid such as naphtha. Lithium ranks 35th in order of abundance of the elements in the crust of the earth. It does not occur in nature in the free state but only in compounds, which are widely distributed. The metal is used as a deoxidizer and to remove unwanted gases during the manufacture of nonferrous castings. Lithium vapor is used to prevent carbon dioxide and oxygen from forming scale in furnac