![](//upload.wikimedia.org/wikipedia/commons/thumb/8/83/Tantalum_single_crystal_and_1cm3_cube.jpg/220px-Tantalum_single_crystal_and_1cm3_cube.jpg) |
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Pronunciation | (TAN-təl-əm) |
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Appearance | gray blue |
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| 180.94788(2)[1] |
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Group | group 5 |
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Period | period 6 |
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Block | d-block |
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Electron configuration | [Xe] 4f14 5d3 6s2 |
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Electrons per shell | 2, 8, 18, 32, 11, 2 |
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Phase at STP | solid |
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Melting point | 3290 K (3017 °C, 5463 °F) |
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Boiling point | 5731 K (5458 °C, 9856 °F) |
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Density (near r.t.) | 16.69 g/cm3 |
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when liquid (at m.p.) | 15 g/cm3 |
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Heat of fusion | 36.57 kJ/mol |
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Heat of vaporization | 753 kJ/mol |
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Molar heat capacity | 25.36 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
3297 |
3597 |
3957 |
4395 |
4939 |
5634 |
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Oxidation states | −3, −1, 0, +1, +2, +3, +4, +5 (a mildly acidic oxide) |
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Electronegativity | Pauling scale: 1.5 |
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Ionization energies | - 1st: 761 kJ/mol
- 2nd: 1500 kJ/mol
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Atomic radius | empirical: 146 pm |
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Covalent radius | 170±8 pm |
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Spectral lines of tantalum |
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Natural occurrence | primordial |
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Crystal structure | body-centered cubic (bcc)[2] α-Ta |
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Crystal structure | tetragonal[2] β-Ta |
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Speed of sound thin rod | 3400 m/s (at 20 °C) |
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Thermal expansion | 6.3 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 57.5 W/(m⋅K) |
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Electrical resistivity | 131 nΩ⋅m (at 20 °C) |
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Magnetic ordering | paramagnetic[3] |
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Molar magnetic susceptibility | +154.0·10−6 cm3/mol (293 K)[4] |
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Young's modulus | 186 GPa |
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Shear modulus | 69 GPa |
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Bulk modulus | 200 GPa |
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Poisson ratio | 0.34 |
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Mohs hardness | 6.5 |
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Vickers hardness | 870–1200 MPa |
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Brinell hardness | 440–3430 MPa |
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CAS Number | 7440-25-7 |
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Discovery | Anders Gustaf Ekeberg (1802) |
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Recognized as a distinct element by | Heinrich Rose (1844) |
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Main isotopes[5] |
Decay |
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abundance |
half-life (t1/2) |
mode |
product |
177Ta |
synth |
56.56 h |
β+ |
177Hf |
178Ta |
synth |
2.36 h |
β+ |
178Hf |
179Ta |
synth |
1.82 y |
ε |
179Hf |
180Ta |
synth |
8.125 h |
ε |
180Hf |
β− |
180W |
180mTa |
0.0120% |
stable |
181Ta |
99.988% |
stable |
182Ta |
synth |
114.43 d |
β− |
182W |
183Ta |
synth |
5.1 d |
β− |
183W |
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Category: Tantalum | references |