Promethium (Pm)

Metallic

Promethium is the only lanthanide with no stable isotopes, glowing faintly blue from its own radioactivity, and with five unpaired 4f electrons, promethium-145 (half-life 17.7 years) is the longest-lived isotope. It is used in nuclear batteries and luminous paint, and was discovered in 1945 from uranium fission products.

Key metrics

Density7.26g/cm³

Melting point1,315K

Boiling point3,273K

Electronegativity1.13Pauling

Discovery

1945discovered

Discovered by: Jacob A. Marinsky
Reactivity profile: Radioactive and reactive
Reactivity: High
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Xe]}\; \textcolor{#a855f7}{4_{f}^{5}}\; \textcolor{#ef4444}{6_{s}^{2}}

[Xe] 4f5 6s2

Wave function

\Psi_{\text{Pm}} \approx \frac{1}{\sqrt{61!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{61}(\mathbf{r}_{61}) \right|

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

Crystal structure

Double Hexagonal Close-Packed

Lattice constantsa 1.00 · b 1.00 · c 2.00

Cell anglesα 90° · β 90° · γ 120°

Coordination number12

Atoms per cell4

Atomic packing factor0.74

Physical properties

Atomic radius: 183 pm
Ionization energy: 540 kJ/mol
Electron affinity: 50 kJ/mol
Crystal structure: Double hexagonal close-packed (dhcp)

Oxidation states

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

1315 K3273 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

528.1nmPm IGreen60%

540.0nmPm IGreen50%

548.2nmPm I (green)Green100%

Dominant line 548.2 nmRange 528–548 nmTransitions 3