Barium (Ba)

Silvery gray; with a pale yellow tint

Barium is a soft metal that makes fireworks green and is swallowed as a chalky drink for X-rays, and with [Xe] 6s², barium's emission spectrum includes strong green lines (524 nm). Barium sulfate is radiopaque (blocks X-rays) and is used as a contrast agent despite barium ions being highly toxic.

Key metrics

Density3.62g/cm³

Melting point1,000K

Boiling point2,170K

Electronegativity0.89Pauling

Discovery

1808discovered

Discovered by: Humphry Davy
Reactivity profile: Reacts with air and water
Reactivity: High
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Xe]}\; \textcolor{#ef4444}{6_{s}^{2}}

[Xe] 6s2

Wave function

\Psi_{\text{Ba}} \approx \frac{1}{\sqrt{56!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{56}(\mathbf{r}_{56}) \right|

Probability density $|\Psi|^2$ across the Ba valence shell.

Crystal structure

Body-Centered Cubic

Lattice constantsa = 1.00

Cell anglesα = β = γ = 90°

Coordination number8

Atoms per cell2

Atomic packing factor0.68

Physical properties

Atomic radius: 253 pm
Ionization energy: 503 kJ/mol
Electron affinity: 14 kJ/mol
Crystal structure: Body-centered cubic (bcc)

Oxidation states

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

1000 K2170 K298 K

Emission spectrum

4 transitions

380450500550600650700780

VioletBlueGreenYellowRed

455.4nmBa I (blue)Blue100%

493.4nmBa I (blue-green)Cyan80%

553.5nmBa I (green)Green60%

578.4nmBa I (yellow)Yellow40%

Dominant line 455.4 nmRange 455–578 nmTransitions 4