Periodic Table


Atomic number: 92
Atomic weight: 238.0289
Symbol: U
Group number: (actinide)
Electronic configuration: [Rn].5f3.6d1.7s2


Uranium is of great interest because of its application to nuclear power and nuclear weapons. Uranium contamination is an emotive environmental problem. It is not particularly rare and is more common than beryllium or tungsten for instance.

General information

Discoveror: Martin Klaproth
Date discovered: 1789
Discovered at: Germany
Meaning of name: Named after "the planet Uranus"

Physical data

Standard state: solid at 298 K
Colour: metallic grey
Density of solid at ambient temperature/kg m-3: 19050
Molar volume/cm3: 12.49

Radii /pm

Atomic: no data
Covalent (single bond):
Pauling radius for the ion [U]-: no data

Valence shell orbital radius maxima (Rmax)
orbital s p d f
radius225.7no data121.352.7


Both values are quoted on the Pauling scale.

Pauling: 1.38
Allred Rochow: 1.22

Crystal Structure

structure: orthorhombic

The following CrystalMaker image represents the solid state structure. For most elements, the most stable allotrope is illustrated. Try WebElements version 2 for interactive virtual reality and CHIME images.


Temperatures (/K)

melting point: 1405.3
boiling point: 4200

Enthalpies /kJ mol-1

fusion: 12
vaporization: 420

single bond enthalpies:
U-F U-Cl U-Br U-I U-U
no data no data no data 343 222

Ionization enthalpies /kJ mol-1

Number Enthalpy


This section gives some data for naturally occurring isotopes.
Nominal mass Accurate mass % natural abundance
234U234.0409468 (24)0.0055 (5)
235U235.0439242 (24)0.7200 (12)
238U238.0507847 (23)99.2745 (60)

Further Information

Copyright 1997 Mark Winter
Department of Chemistry at the University of Sheffield, Sheffield S3 7HF, England.

The current version of this document is at http://www.shef.ac.uk/~chem/web-elements-I/U.html