Uranium

protactinium ← uranium → neptunium Nd ↑ U ↓ —

Atomic properties Atomic number 92 Standard atomic weight 238.028 91(3) Electron configuration [Rn] 5f3 6d1 7s2 Physical properties Melting point 1130 °C (1400 K) Boiling point 3930 °C (4200 K) Density 19.05 g cm−3 Electric resistivity 28 × 10−6 Ω cm Chemical properties Electronegativity 1.38 (Pauling) Ionization energy 6.19 eV, 597 kJ mol−1 Atomic radii Covalent radius 196 pm Metallic radius 156 pm Ionic radius 87 pm (U6+, Oh) 103 pm (U4+, Oh) Thermodynamic properties Standard entropy 50.20(20) J K−1 mol−1 Enthalpy change of atomization 533(8) kJ mol−1 Entropy change of atomization 149.59(22) J K−1 mol−1 Enthalpy change of fusion 12.6 kJ mol−1 Enthalpy change of vaporization 417 kJ mol−1 Hazards GHS pictograms GHS signal word DANGER GHS hazard statements H330, H300, H373, H413 Miscellaneous CAS number 7440-61-1 EC number 231-170-6 Where appropriate, and unless otherwise stated, data are given for 100 kPa (1 bar) and 298.15 K (25 °C).

Uranium (symbol: U) is a chemical element, a member of the actinoid series. Although all isotopes of uranium are unstable, three have sufficiently long half-lives that a substantial amount of primordial uranium has survived since the formation of the Solar System. The natural material is only very slightly radioactive, and uranium and its compounds have a number of commercial uses, although some precautions must be taken over its decay products.

Uranium was identified as a new element in 1789 by Martin Heinrich Klaproth, and named after the planet Uranus, which had been discovered by William Herschel in 1781. Its chemistry resembles that of molybdenum and tungsten, with a preponderance of the +4 and +6 oxidation states, and periodic tables from before the Second World War often placed uranium as a transition metal.

Notes and references

Further reading

• Grenthe, Ingmar; Drożdżyński, Janusz; Fujino, Takeo; Buck, Edgar C.; Albrecht-Schmitt, Thomas E.; Wolf, Stephen F. Uranium. In The Chemistry of the Actinide and Transactinide Elements, 3rd ed.; Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean, Eds.; Springer: Dordrecht, the Netherlands, 2006; Vol. 1, Chapter 5, pp 253–698. doi:10.1007/1-4020-3598-5_5, <http://radchem.nevada.edu/classes/rdch710/files/uranium.pdf>.

External links

• WebElements