In 1774, Carl Wilhelm Scheele showed that barium oxide is a distinct compound. Barium was first isolated by Sir Humphry Davy, an English chemist, in 1808 through the electrolysis of molten barium salts.
Atomic number: 56
Atomic weight: 137.33
Group, period, block: 2, 6, s
Color: silvery gray
Classification: alkaline earth metals
Electron configuration: 6s2
Density: 3.51 g/cm-3
Melting point: 1000 K, 727 °C, 1341 °F
Boiling point: 2170 K, 1897 °C, 3447 °F
Oxidation states: +2
Electronegativity: 0.89 (Pauling scale)
Ionization energies: 1st: 502.9 kJ·mol-1
Covalent radius: 215±11 pm
Van der Waals radius: 268 pm
There are seven naturally occurring isotopes of barium exist, 130Ba, 132Ba, 134Ba, 135Ba, 136Ba, 137Ba, and <138Ba.