Thorium, 90 Th General properties Pronunciation Template:Infobox element/pronunciation Appearance silvery, often with black tarnish 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)Thorium in the periodic table Template:Infobox element/periodic table Atomic number (Z ) 90 Group Template:Infobox element/group Period period 7 Block f-block Element category Template:Infobox element/category format Electron configuration [Rn ] 6d2 7s2 Electrons per shell
2, 8, 18, 32, 18, 10, 2 Physical properties Phase at STP solid Melting point 2023 K (1750 °C, 3182 °F) Boiling point 5061 K (4788 °C, 8650 °F) Density (near r.t. ) 11.7 g/cm3 Heat of fusion 13.81 kJ/mol [[Enthalpy of vaporization|Heat of Template:Engvar ]] 514 kJ/mol Molar heat capacity 26.230 J/(mol·K) [[Vapor pressure|Template:Engvar pressure ]] Atomic properties Oxidation states Template:Infobox element/symbol-to-oxidation-state Electronegativity Pauling scale: 1.3 [[Ionization energy|Template:Engvar energies]] 1st: 587 kJ/mol 2nd: 1110 kJ/mol 3rd: 1930 kJ/mol Atomic radius empirical: 179.8 pm Covalent radius 206±6 pm Template:Infobox element/spectral lines Other properties Crystal structure Template:Infobox element/crystal structure Speed of sound thin rod 2490 m/s (at 20 °C) Thermal expansion 11.0 µm/(m·K) (at 25 °C) Thermal conductivity 54.0 W/(m·K) Electrical resistivity 157 nΩ·m (at 0 °C) Magnetic ordering paramagnetic [1] Magnetic susceptibility 132.0·10−6 cm3 /mol (293 K)[2] Young's modulus 79 GPa Shear modulus 31 GPa Bulk modulus 54 GPa Poisson ratio 0.27 Mohs hardness 3.0 Vickers hardness 295–685 MPa Brinell hardness 390–1500 MPa CAS Number 7440-29-1 History Naming after Thor , the Norse god of thunder Discovery Jöns Jakob Berzelius (1829) Main isotopes of thorium Template:Infobox element/isotopes table | references
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