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Pronunciation | (THOR-ee-əm) |
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Appearance | silvery |
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| 232.0377(4)[1] |
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Atomic number (Z) | 90 |
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Group | f-block groups (no number) |
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Period | period 7 |
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Block | f-block |
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Electron configuration | [Rn] 6d2 7s2 |
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Electrons per shell | 2, 8, 18, 32, 18, 10, 2 |
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Phase at STP | solid |
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Melting point | 2023 K (1750 °C, 3182 °F) |
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Boiling point | 5061 K (4788 °C, 8650 °F) |
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Density (near r.t.) | 11.7 g/cm3 |
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Heat of fusion | 13.81 kJ/mol |
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Heat of vaporization | 514 kJ/mol |
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Molar heat capacity | 26.230 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
2633 |
2907 |
3248 |
3683 |
4259 |
5055 |
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Oxidation states | −1,[2] +1, +2, +3, +4 (a weakly basic oxide) |
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Electronegativity | Pauling scale: 1.3 |
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Ionization energies | - 1st: 587 kJ/mol
- 2nd: 1110 kJ/mol
- 3rd: 1930 kJ/mol
-
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Atomic radius | empirical: 179.8 pm |
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Covalent radius | 206±6 pm |
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Spectral lines of thorium |
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Natural occurrence | primordial |
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Crystal structure | face-centered cubic (fcc) |
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Speed of sound thin rod | 2490 m/s (at 20 °C) |
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Thermal expansion | 11.0 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 54.0 W/(m⋅K) |
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Electrical resistivity | 157 nΩ⋅m (at 0 °C) |
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Magnetic ordering | paramagnetic[3] |
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Molar magnetic susceptibility | 132.0×10−6 cm3/mol (293 K)[4] |
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Young's modulus | 79 GPa |
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Shear modulus | 31 GPa |
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Bulk modulus | 54 GPa |
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Poisson ratio | 0.27 |
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Mohs hardness | 3.0 |
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Vickers hardness | 295–685 MPa |
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Brinell hardness | 390–1500 MPa |
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CAS Number | 7440-29-1 |
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Naming | after Thor, the Norse god of thunder |
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Discovery | Jöns Jakob Berzelius (1829) |
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Main isotopes[5] |
Decay |
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abundance |
half-life (t1/2) |
mode |
product |
227Th |
trace |
18.68 d |
α |
223Ra |
228Th |
trace |
1.9116 y |
α |
224Ra |
229Th |
trace |
7917 y[6] |
α |
225Ra |
230Th |
0.02% |
75400 y |
α |
226Ra |
231Th |
trace |
25.5 h |
β− |
231Pa |
232Th |
100.0% |
1.405×1010 y |
α |
228Ra |
234Th |
trace |
24.1 d |
β− |
234Pa |
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Category: Thorium | references |