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Pronunciation | (HAF-nee-əm) |
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Appearance | steel gray |
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| 178.486(6)[1] |
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Atomic number (Z) | 72 |
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Group | group 4 |
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Period | period 6 |
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Block | d-block |
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Electron configuration | [Xe] 4f14 5d2 6s2 |
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Electrons per shell | 2, 8, 18, 32, 10, 2 |
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Phase at STP | solid |
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Melting point | 2506 K (2233 °C, 4051 °F) |
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Boiling point | 4876 K (4603 °C, 8317 °F) |
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Density (near r.t.) | 13.31 g/cm3 |
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when liquid (at m.p.) | 12 g/cm3 |
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Heat of fusion | 27.2 kJ/mol |
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Heat of vaporization | 648 kJ/mol |
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Molar heat capacity | 25.73 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
2689 |
2954 |
3277 |
3679 |
4194 |
4876 |
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Oxidation states | −2, 0, +1, +2, +3, +4 (an amphoteric oxide) |
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Electronegativity | Pauling scale: 1.3 |
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Ionization energies | - 1st: 658.5 kJ/mol
- 2nd: 1440 kJ/mol
- 3rd: 2250 kJ/mol
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Atomic radius | empirical: 159 pm |
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Covalent radius | 175±10 pm |
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Spectral lines of hafnium |
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Natural occurrence | primordial |
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Crystal structure | hexagonal close-packed (hcp) |
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Speed of sound thin rod | 3010 m/s (at 20 °C) |
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Thermal expansion | 5.9 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 23.0 W/(m⋅K) |
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Electrical resistivity | 331 nΩ⋅m (at 20 °C) |
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Magnetic ordering | paramagnetic[2] |
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Molar magnetic susceptibility | +75.0×10−6 cm3/mol (at 298 K)[3] |
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Young's modulus | 78 GPa |
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Shear modulus | 30 GPa |
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Bulk modulus | 110 GPa |
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Poisson ratio | 0.37 |
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Mohs hardness | 5.5 |
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Vickers hardness | 1520–2060 MPa |
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Brinell hardness | 1450–2100 MPa |
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CAS Number | 7440-58-6 |
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Naming | after Hafnia. Latin for: Copenhagen, where it was discovered |
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Prediction | Dmitri Mendeleev (1869) |
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Discovery and first isolation | Dirk Coster and George de Hevesy (1922) |
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Main isotopes[4] |
Decay |
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abundance |
half-life (t1/2) |
mode |
product |
172Hf |
synth |
1.87 y |
ε |
172Lu |
174Hf |
0.16% |
7.0×1016 y[5] |
α |
170Yb |
176Hf |
5.26% |
stable |
177Hf |
18.6% |
stable |
178Hf |
27.3% |
stable |
178m2Hf |
synth |
31 y |
IT |
178Hf |
179Hf |
13.6% |
stable |
180Hf |
35.1% |
stable |
182Hf |
synth |
8.9×106 y |
β− |
182Ta |
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Category: Hafnium | references |