Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Because of its high chemical reactivity barium is never found in nature as a free element. Its hydroxide was known in pre-modern history as baryta; this substance does not occur as a mineral, but can be prepared by heating barium carbonate.Symbol: Ba
Electron configuration: Xe 6s2
Atomic number: 56
Discovered: 1808
Atomic mass: 137.327 ± 0.007 u
Discoverer: Carl Wilhelm Scheele