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Pronunciation | [1] |
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Appearance | hard lustrous bluish gray metal |
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| 58.933194(3)[2] |
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Atomic number (Z) | 27 |
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Group | group 9 |
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Period | period 4 |
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Block | d-block |
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Electron configuration | [Ar] 3d7 4s2 |
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Electrons per shell | 2, 8, 15, 2 |
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Phase at STP | solid |
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Melting point | 1768 K (1495 °C, 2723 °F) |
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Boiling point | 3200 K (2927 °C, 5301 °F) |
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Density (near r.t.) | 8.90 g/cm3 |
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when liquid (at m.p.) | 8.86 g/cm3 |
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Heat of fusion | 16.06 kJ/mol |
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Heat of vaporization | 377 kJ/mol |
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Molar heat capacity | 24.81 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
1790 |
1960 |
2165 |
2423 |
2755 |
3198 |
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Oxidation states | −3, −1, 0, +1, +2, +3, +4, +5[3] (an amphoteric oxide) |
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Electronegativity | Pauling scale: 1.88 |
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Ionization energies | - 1st: 760.4 kJ/mol
- 2nd: 1648 kJ/mol
- 3rd: 3232 kJ/mol
- (more)
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Atomic radius | empirical: 125 pm |
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Covalent radius | Low spin: 126±3 pm High spin: 150±7 pm |
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Spectral lines of cobalt |
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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 | 4720 m/s (at 20 °C) |
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Thermal expansion | 13.0 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 100 W/(m⋅K) |
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Electrical resistivity | 62.4 nΩ⋅m (at 20 °C) |
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Magnetic ordering | ferromagnetic |
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Young's modulus | 209 GPa |
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Shear modulus | 75 GPa |
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Bulk modulus | 180 GPa |
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Poisson ratio | 0.31 |
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Mohs hardness | 5.0 |
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Vickers hardness | 1043 MPa |
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Brinell hardness | 470–3000 MPa |
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CAS Number | 7440-48-4 |
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Discovery and first isolation | Georg Brandt (1735) |
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Main isotopes[4] |
Decay |
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abundance |
half-life (t1/2) |
mode |
product |
56Co |
synth |
77.236 d |
β+ |
56Fe |
57Co |
synth |
271.811 d |
ε |
57Fe |
58Co |
synth |
70.844 d |
β+ |
58Fe |
59Co |
100% |
stable |
60Co |
trace |
5.2714 y |
β−100% |
60Ni |
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Category: Cobalt | references |