BARIUM
ALKALINE EARTH METAL
| 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(7) |
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. The price of 99.2 % pure barium pieces is 1347.20 € for 1000 g.
| 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 |
| First ionization energy / kJ mol-1: | 502.86 |
| Second ionization energy / kJ mol-1: | 965.24 |
| Third ionization energy / kJ mol-1: | - |
| in the atmosphere / ppm: | - |
| in the Earth's crust / ppm: | 250 |
| in the oceans / ppm: | 0.03 |
| Crystal structure: | body-centered cubic |
| Unit-cell dimensions / pm: | a=502.5 |
| Space group: | Im3m |
| Isotope | Relative atomic mass | Mass percent (%) |
|---|---|---|
| 130Ba | 129.906310(7) | 0.106(2) |
| 132Ba | 131.905056(3) | 0.101(2) |
| 134Ba | 133.904503(3) | 2.417(27) |
| 135Ba | 134.905683(3) | 6.592(18) |
| 136Ba | 135.904570(3) | 7.854(36) |
| 137Ba | 136.905821(3) | 11.23(4) |
| 138Ba | 137.905241(3) | 71.70(7) |
| Balanced half-reaction | Eo / V | |
|---|---|---|
| Ba2+ + 2e- → Ba(s) | - 2.906 | |
| BaO + 2H+ + 2e- → Ba(s) + H2O | - 2.166 |
| 55 Caesium | ← | 56 Barium | → | 57 Lanthanum |
Citing this page:
Generalic, Eni. "Barium." EniG. Periodic Table of the Elements. KTF-Split, 18 Jan. 2024. Web. {Date of access}. <https://www.periodni.com/ba.html>.
