| Tantalum - Ta
CAS: 7440-25-7 Description:Gray, heavy, hard but ductile metal Classification: Transition Metal Date of Discovery: 1802 Discoverer: Anders Ekeberg Name Origin: Greek Tantalos, mythological father of Niobe |
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Atomic Number: 73
Number of Neutrons: 108 Atomic Mass: 180.9479(1) amu Melting Point: 3017 °C Boiling Point: 5548 ± 100 °C Density (293 K): 16.654 g/cm3 Atomic volume: 10.90 cm3/mol Electrical resistivity: 0.0761 10-6/cm 
Thermal conductivity: 0.575 W/cmK Enthalpy of atomization: 782 kJ/mol (est.) Enthalpy of vaporization: 743.0 kJ/mol Enthalpy of fusion: 31.60 kJ/mol Specific heat capacity: 0.14 J/gK |
Energy levels: 2-8-18-32-11-2
Electron configuration: [Xe]4f 145d36s2 Crystal Structure: Cubic body centered Atomic radius: 2.09 Å Covalent radius: 1.34 Å Oxidation States: +2(?), +3, +4(?), or +5 Electronegativity, Pauling: 1.5 Electron affinity: 0.322 eV First ionization energy: 7.89 eV 2nd ionization energy: 3rd ionization energy: Polarizability: 13.1 10-24cm3 |
| Isotope | Natural Abundance | Atomic Mass | Half-life | Decay Mode | Spin |
| 156Ta | 155.972 | > 0.01 s |  +; p |
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| 157Ta | 156.968 | 5 ms |  |
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| 158Ta | 157.9664 | 37 ms | |
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| 159Ta | 158.9629 | 0.6 s | +, EC; |
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| 160Ta | 159.9615 | 1.4 s | +, EC; |
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| 161Ta | 160.9584 | 2.9 s | +, EC; |
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| 162Ta | 161.9564 | 4 s | EC | ||
| 163Ta | 162.9544 | 10.6 s | EC | ||
| 164Ta | 163.9536 | 14.2 s | +; |
3+ | |
| 165Ta | 164.9508 | 31 s | EC, + |
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| 166Ta | 165.9505 | 34 s | +; EC |
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| 167Ta | 166.9486 | 1.4 m | +, EC |
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| 168Ta | 167.9478 | 2.4 m | +; EC |
3+ | |
| 169Ta | 168.9459 | 4.9 m | +, EC |
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| 170Ta | 169.9461 | 6.5 m | +; EC |
(3+) | |
| 171Ta | 170.9445 | 23.3 m | +, EC |
(5/2-) | |
| 172Ta | 171.9447 | 36.8 m | +; EC |
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| 173Ta | 172.9446 | 3.6 h | +; EC |
(5/2-) | |
| 174Ta | 173.9442 | 1.12 h | +; EC |
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| 175Ta | 174.9437 | 10.5 h | EC | 7/2+ | |
| 176Ta | 175.9447 | 8.1 h | EC | 1- | |
| 177Ta | 176.944472 | 2.356 d | EC | 7/2+ | |
| 178mTa | 2.4 h | EC | (7-) | ||
| 178Ta | 177.9458 | 9.29 m | EC; + |
1+ | |
| 179Ta | 178.94593 | 1.8 y | EC | 7/2+ | |
| 180mTa | 0.012(2) | > 1.2 x 1015 y | (9-) | ||
| 180Ta | 179.947466 | 8.15 h | EC; - |
1+ | |
| 181Ta | 98.988(2) | 180.947996 | Stable | 7/2+ | |
| 182mTa | 15.8 m | IT | 10- | ||
| 182Ta | 181.950152 | 114.43 d | - |
3- | |
| 183Ta | 182.951373 | 5.1 d | - |
7/2+ | |
| 184Ta | 183.95401 | 8.7 h | - |
(5-) | |
| 185Ta | 184.95556 | 49 m | - |
(7/2+) | |
| 186Ta | 185.9586 | 10.5 m | - |
(3-) | |
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Discovered in 1802 by Ekeberg, but many chemists thought niobium and tantalum were identical elements until Rose, in 1844, and Marignac, in 1866 showed that niobic and tantalic acids were two different acids. The early investigators only isolated the impure metal. The first relatively pure ductile tantalum was produced by von Bolton in 1903. Tantalum occurs principally in the mineral columbite-tantalite (Fe, Mn)(Nb, Ta)2O6. Tantalum ores are found in Australia, Brazil, Mozambique, Thailand, Portugal, Nigeria, Zaire, and Canada. Separation of tantalum from niobium requires several complicated steps. Several methods are used to commercially produce the element, including electrolysis of molten potassium fluorotantalate, reduction of potassium fluorotantalate with sodium, or reacting tantalum carbide with tantalum oxide. Thirty-four isotopes and isomers of tantalum are known to exist. Natural tantalum contains two isotopes, one of which is radioactive with a very long half-life. Tantalum is a gray, heavy, and very hard metal. When pure, it is ductile and can be drawn into fine wire, which is used as a filament for evaporating metals such as aluminum. Tantalum is almost completely immune to chemical attack at temperatures below 150 °C, and is attacked only by hydrofluoric acid, acidic solutions containing the fluoride ion, and free sulfur trioxide. Alkalis attack it only slowly. At high temperatures, tantalum becomes much more reactive. The element has a melting point
exceeded only by tungsten and rhenium. Tantalum is used to make a variety of alloys with desirable properties such as high melting point, high strength, good ductility, etc. Scientists at Los Alamos have produced a tantalum carbide graphite composite material, which is said to be one of the hardest materials ever made. The compound has a melting point of 3738 °C. Tantalum has good "gettering" ability at high temperatures, and tantalum oxide films are stable and have good rectifying and dielectric properties. Tantalum is used to make electrolytic capacitors and vacuum furnace parts, which account
for about 60% of its use. The metal is also widely used to fabricate chemical process equipment, nuclear reactors, and aircraft and missile parts. Tantalum is completely immune to body liquids and is a nonirritating metal. It has, therefore, found wide use in making surgical appliances. Tantalum oxide is used to make special glass with high index of refraction for camera lenses. The metal has many other uses.
LINKS: COMETEC: Background Knowledge Cutting Tool Engineering - Tantalum and Niobium Minerals Containing Tantalum Material Safety Data Sheet - Tantalum Tantalum Mining Corporation of Canada Ltd Tantalum : Performance In Various Corrosives Titanium Tantalum Products Return
Sources for the information on this website include: Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998. |
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