Lithium (Li) is a chemical element that has atomic number 3 in the periodic table of elements.
Lithium belongs to the alkali metals and has the smallest mass density of 5 g/ccm, which is determined from the ratio of mass to volume. Lithium is silvery white and quite soft for a metal.
Lithium does not occur elementally in nature because its surface oxidizes to lithium oxide (Li2O) even at low humidity, and to lithium nitride (Li3N) in dry air. Inelectronics, lithium is used mainly in batteries and rechargeable batteries because of its low specific weight, which is characterized by a high energy density.