Uranium (U)

Uranium is an actinide with atomic number 92, in period 7, in the f-block of the periodic table. Its atomic mass is 238.02891 u and its electron configuration is [Rn] 5f³ 6d¹ 7s². Solid at 25 °C.

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Key facts

Atomic number	92
Atomic mass	238.02891 u
Category	Actinide
Period	7
Group	f-block, no group number
Block	f
Electron configuration	[Rn] 5f³ 6d¹ 7s²
Electrons per shell	2, 8, 18, 32, 21, 9, 2
Electronegativity (Pauling)	1.38
Oxidation states	+1, +2, +3, +4, +5, +6common in bold
State at 25 °C	Solid
Melting point	1408 K1134.85 °C
Boiling point	4404 K4130.85 °C
Density	19.1 g/cm³

Atomic properties

First ionization energy	6.194 eV
Electron affinity	---
Atomic radius	138 pm
Covalent radius	196 pm
Van der Waals radius	240 pm
Common ions	U⁶⁺, U⁴⁺
Protons, neutrons, electrons	92, 146, 92

Physical and thermal properties

Molar volume	12.49 cm³/mol
Heat of fusion	14 kJ/mol
Heat of vaporization	420 kJ/mol
Specific heat	116 J/(kg·K)
Thermal conductivity	27 W/(m·K)
Thermal expansion	1.39 × 10⁻⁵ K⁻¹
Mohs hardness	6
Young’s modulus	208 GPa
Crystal structure	Base orthorhombic
Magnetic type	Paramagnetic

Identification and history

CAS number	7440-61-1
Latin name	Uranium
Discovered by	M. H. Klaproth · 1789
Named by	---

Natural isotopes

Isotope	Mass (u)	Abundance
²³⁴U	234.04095	0.0054 %
²³⁵U	235.043928	0.7204 %
²³⁸U	238.050787	99.2742 %

Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.

A dash (---) means there is no reliable published measurement. The app never makes one up.

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