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Thorium
Electron Configuration 2,8,18,32,18,10,2
Electron Configuration [Rn] 6d2 7s2
Ground state 3F2
Atomic Volume 19.9 g/cm3
Electronegativity 1.3
Magnetic ordering No data
Mass magnetic susceptibility 5.3 x 10-9
Molar magnetic susceptibility 1.23 x 10-9
Speed of sound 2490 m s-1
Thermal Properties
Enthalpy of Atomization 565 kJ mol-1 @25°C
Enthalpy of Fusion 19.2 kJ mol-1
Enthalpy of Vaporisation 513.7 kJ mol-1
Heat Capacity 26.230 J mol-1 K-1
Thermal Conductivity 54.0 W m-1 K-1
Thermal Expansion 11.0 μm m-1 K-1
Hardness
Brinell hardness 400 MPa
Mohs hardness 3.0
Vickers hardness 350 MPa
Elastic Properties
Bulk modulus 54 GPa
Poisson ratio 0.27
Shear modulus 31 GPa
Young's modulus 79 GPa
Electrical Properties
Electrical resistivity 1.5 x 10-7 Ω m
Electrical conductivity No data.
Chemical Properties
Electrochemical Equivalent 2.1643 g Ah-1
Electron Work Function 3.41 eV
Valence Electron Potential (-eV) 59.3
Ionization Potential  
First 6.08
Second 11.504
Third 20.003
Energy Levels
Kα1 (intensity 0) 93.35 KeV
Kα2 (intensity 0) 89.953 KeV
Kβ1 (intensity 0) 105.609 KeV
Lα1 (intensity 100) 12.9687 KeV
Lα2 (intensity 10) 12.8096 KeV
Lβ1 (intensity 38) 16.2022 KeV
Lβ2 (intensity 14) 15.6237 KeV
Lβ3 (intensity 2) 16.4212 KeV
Lβ4 (intensity 2) 15.6385 KeV
Lγ1 (intensity 8) 18.9825 KeV
Lγ2 (intensity 2.7) 19.2987 KeV
Lγ3 (intensity 2) 14.505 KeV
Ll (intensity 6) 11.1189 KeV
Atomic Radii
Empirical 180 pm
Bohr Radius No data.
Covalent Radius No data.
Van der Waals No data.
Triple covalent 136 pm
Metallic 179 pm
Ionic Radii (Å)
Charge Coordination Crystal Ionic Key
VI 1.08 0.94 C
VIII 1.19 1.05 RC
IX 1.23 1.09 *
X 1.27 1.13 E
XI 1.32 1.18 C
XII 1.35 1.21 C
R, From r3 vs V plots.
C, Calculated from bond length - bond strength equations.
E, Estimated.
*, Most Reliable.
M, From Metallic Oxides.
A, Ahrens (1952) Ionic radius.
P, Pauling's (1960) Crystal Radius.
Oxidation States
Main Th+4
Other Th+2, Th+3
Ionisation Energies (kJ mol-1) show graph
M - M+ 587
M+ - M2+ 1110
M2+ - M3+ 1978
M3+ - M4+ 2780
Vapour Pressure
P (Pa) 1 10 100 1K 10K 100K
T (K) 2633 2907 3248 3683 4259 5055
Crystal Structure
Structure Cubic close packed
a = 508.42 pm
b = 508.42 pm
c = 508.42 pm
α = 90°
β = 90°
γ = 90°