Atomic number:56

Group numbers:2

Period:6

Electronic configuration:[Xe] 6s²

Formal oxidation number:+2

Electronegativities:0.89

Atomic radius / pm:217.4

Relative atomic mass:137.327 ± 0.007

 

Barium was discovered by Sir Humphry Davy (GB) in 1808. The origin of the name comes from the Greek word barys meaning heavy. It is a soft, slightly malleable, silvery-white metal. Barium oxidises in air and reacts with water. Soluble compounds are toxic by ingestion. Barium is found in barytine (BaSO4) and witherite (BaCO3), it is never found in pure form due to its reactivity. Barium must be stored under kerosene to remain pure. Barite, or barium sulfate (BaSO4) is used as a filter for rubber, plastics and resins. It is insoluble in water and so is used in X-rays of the digestive system. Barium nitrate, Ba(NO3)2, burns brilliant green and is used in fireworks.

Density / g dm^-3:3594 (293 K)

 3325 (m.p.)

Molar volume / cm³mol^-1:38.21 (293 K)

 41.30 (m.p.)

Electrical resistivity / μΩcm:50 (20 °C)

Thermal conductivity / W m^-1K^-1:18.4

Melting point / °C:727

Boiling point / °C:1897

Heat of fusion / kJ mol^-1:7.66

Heat of vaporization / kJ mol^-1:150.9

Heat of atomization / kJ mol^-1:180.7

1st ionization energy / kJ mol^-1:502.86

2nd ionization energy / kJ mol^-1:965.24

3rd ionization energy / kJ mol^-1:-

in the atmosphere / ppm:-

in the Earth's crust / ppm:250

in the oceans / ppm:0.03