Radium (Ra)

Silvery-white metal

Radium was once painted on watch dials to glow in the dark, killing the workers who licked their brushes, and with [Rn] 7s², radium-226 (half-life 1600 years) was discovered by Marie and Pierre Curie in 1898. Its intense radioactivity (160 TBq/g) made it a medical treatment before its extreme toxicity was understood.

Key metrics

Density5.5g/cm³

Melting point973K

Boiling point2,010K

Electronegativity0.9Pauling

Discovery

1898discovered

Discovered by: Marie Curie
Reactivity profile: Highly radioactive
Reactivity: High
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Rn]}\; \textcolor{#ef4444}{7_{s}^{2}}

[Rn] 7s2

Wave function

\Psi_{\text{Ra}} \approx \frac{1}{\sqrt{88!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{88}(\mathbf{r}_{88}) \right|

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

Crystal structure

Face-Centered Cubic

Lattice constantsa = 1.00

Cell anglesα = β = γ = 90°

Coordination number12

Atoms per cell4

Atomic packing factor0.74

Physical properties

Atomic radius: 215 pm
Ionization energy: 509 kJ/mol
Electron affinity: 10 kJ/mol
Crystal structure: Face-centered cubic

Oxidation states

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

973 K2010 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

381.4nmRa I (UV)UV40%

453.3nmRa IBlue70%

482.6nmRa I (blue)Blue100%

Dominant line 482.6 nmRange 381–483 nmTransitions 3