056Alkaline earth metal · Group 2 · Period 6

Barium

Barium (Ba) is element 56, a alkaline earth metal in the s-block — group 2, period 6. It is a solid at room temperature with 6 electron shells (2, 8, 18, 18, 8, 2) and an atomic mass of 137.3277 u.

Atomic mass: 137.3 u
Phase · STP: solid
Melting: 1000 K · 727 °C
Boiling: 2118 K · 1845 °C
Electronegativity: 0.89
Density: 3.51 g/cm³

Photograph — Hi-Res Images ofChemical Elements, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: https://images-of-elements.com/barium.php

Identity

Atomic number: 56
Standard atomic weight: 137.3 u
Category: Alkaline earth metal
Group: 2 · Alkaline earth metals
Period: 6
Block: s-block
Oxidation states: +2

Physical properties

Melting point: 1000 K · 727 °C
Boiling point: 2118 K · 1845 °C
Density: 3.51 g/cm³
Molar heat capacity: 28.07 J/(mol·K)
Atomic radius: 268 pm
Electron affinity: 13.954 kJ/mol

Atomic structure

56protons

81neutrons

56electrons

2valence e⁻

Noble-gas notation: [Xe] 6s2
Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
Electrons per shell: 2, 8, 18, 18, 8, 2

Periodic trends

Where Barium ranks across all 118 elements.

Electronegativity0.89

Ionization energy502.9 kJ/mol

Electron affinity13.954 kJ/mol

Density3.51 g/cm³

Atomic radius268 pm

Ionization energies

Energy to remove each successive electron (kJ/mol).

502.9

965.2

3.6k

Successive ionization energies (kJ/mol, log scale).

Discovery

Discovered: 1808
Discovered by: Carl Wilhelm Scheele
Named by: —
Appearance: —