Sodium, Na /ˈsoʊdiəm / (Latin Natrium, Arabic noun natrun, Greek nitron, originally – sodium soda) is a chemical element of group I of the periodic table of Mendeleev; atomic number 11, atomic mass 22.98977; refers to alkali metals. One stable isotope, 23Na, occurs in nature. Sodium compounds have been known since ancient times. Metallic sodium was first obtained (1807) by the English scientist G. Devy.