Uranium(U)
Uranium is an actinide metal used as nuclear fuel. Its chemistry includes multiple oxidation states, notably +4 and +6.
KEY PROPERTIES
Electron configuration & shells
[Rn] 5f³ 6d¹ 7s²
Shell model is schematic — see lesson on atomic structure for orbitals. Oxidation states: +4, +6. Common ions: U⁴⁺, UO₂²⁺.
Measured properties
Values at stated conditions; missing data shown as “—”. Radii distinguished by type; densities at stated phase/temperature.
- Electronegativity (Pauling)
- 1.38
- First ionization energy
- 598 kJ·mol⁻¹ (first ionization, gas phase)
- Atomic radius
- 175 pm (calculated)
- Covalent radius
- 196 pm (covalent)
- Van der Waals radius
- 175 pm (van der Waals)
- Density
- 18.95 g·cm⁻³ (solid at 20 °C, 1 atm)
- Melting point
- 1405.3 K (1 atm)
- Boiling point
- 4404 K (1 atm)
Standard conditions: 1 atm unless noted. Values with null are not established or not comparable across allotropes. Radii are distinguished by type. Densities at stated phase/temperature.
| Mass number | Abundance | Stability | Half-life |
|---|---|---|---|
| 238 | 99.2745% | radioactive | 4.468×10⁹ y |
| 235 | 0.72% | radioactive | 7.04×10⁸ y |
| 234 | 0.005% | radioactive | 2.455×10⁵ y |
Isotopic abundances are natural terrestrial values where applicable; synthetic isotopes shown as trace.
Occurrence & uses
Trace in nature; primarily obtained from uranium ores.
- Nuclear fuel
- Nuclear weapons (historical)
- Research
Discovery
Martin Heinrich Klaproth — 1789
Safety
RELATED CONTENT
SOURCES
- [nist-atomic-weights]nist-atomic-weights (2022)/#nist-atomic-weights
- [nist-2022]nist-2022 (2022)/#nist-2022
- [iupac-gold]iupac-gold (2022)/#iupac-gold
Last reviewed: 2026-08-22 • Reviewer: dr-example