Uranium, 92 U General properties Pronunciation Template:Infobox element/pronunciation Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Standard atomic weight (A r, standard ) Template:Infobox element/standard atomic weight Mass number Template:Infobox element/symbol-to-most-stable-isotope (most stable isotope)Uranium in the periodic table Template:Infobox element/periodic table Atomic number (Z ) 92 Group Template:Infobox element/group Period period 7 Block f-block Element category Template:Infobox element/category format Electron configuration [Rn ] 5f3 6d1 7s2 Electrons per shell
2, 8, 18, 32, 21, 9, 2 Physical properties Phase at STP solid Melting point 1405.3 K (1132.2 °C, 2070 °F) Boiling point 4404 K (4131 °C, 7468 °F) Density (near r.t. ) 19.1 g/cm3 when liquid (at m.p. ) 17.3 g/cm3 Heat of fusion 9.14 kJ/mol [[Enthalpy of vaporization|Heat of Template:Engvar ]] 417.1 kJ/mol Molar heat capacity 27.665 J/(mol·K) [[Vapor pressure|Template:Engvar pressure ]] Atomic properties Oxidation states Template:Infobox element/symbol-to-oxidation-state Electronegativity Pauling scale: 1.38 [[Ionization energy|Template:Engvar energies]] 1st: 597.6 kJ/mol 2nd: 1420 kJ/mol Atomic radius empirical: 156 pm Covalent radius 196±7 pm Van der Waals radius 186 pm Template:Infobox element/spectral lines Other properties Crystal structure Template:Infobox element/crystal structure Speed of sound thin rod 3155 m/s (at 20 °C) Thermal expansion 13.9 µm/(m·K) (at 25 °C) Thermal conductivity 27.5 W/(m·K) Electrical resistivity 0.280 µΩ·m (at 0 °C) Magnetic ordering paramagnetic Young's modulus 208 GPa Shear modulus 111 GPa Bulk modulus 100 GPa Poisson ratio 0.23 Vickers hardness 1960–2500 MPa Brinell hardness 2350–3850 MPa CAS Number 7440-61-1 History Naming after planet Uranus , itself named after Greek god of the sky Uranus Discovery Martin Heinrich Klaproth (1789) First isolation Eugène-Melchior Péligot (1841) Main isotopes of uranium Template:Infobox element/isotopes table | references
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↑ Morss, L.R.; Edelstein, N.M.; Fuger, J., eds. (2006). The Chemistry of the Actinide and Transactinide Elements (3rd ed.). Netherlands: Springer. ISBN 9048131464 .