Periodic table / Alkaline earth metals
56Barium
Barium is an alkaline earth metal in group 2, period 6. At 25 °C it is a solid.
- Symbol
- Ba
- Atomic number
- 56 protons in the nucleus
- Standard atomic weight
- 137.33 ± 0.01
- Electron configuration
- [Xe] 6s2
- Electrons in each shell
- 2, 8, 18, 18, 8, 2
- Group, period, block
- 2, 6, s
- Family
- Alkaline earth metals
- State at 25 °C
- solid
- Electronegativity
- 0.89 (Pauling scale)
- First ionisation energy
- 502.8 kJ/mol (5.2116646 eV)
Where these numbers come from
Atomic weight: IUPAC CIAAW, abridged standard atomic weights 2024. Electron configuration and ionisation energy: NIST Atomic Spectra Database. Family, state and electronegativity: PubChem. See Sources. Melting points, boiling points and densities are left out for now: published values differ between sources, and we will add them once each has been checked.