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Chemical Fact Sheet

Tantalum

Chemical Abstract Number (CAS #) 7440-25-7
Analytical Methods 200.7 - 200.8 - 6010 - 6020
Atomic Symbol Ta

Synopsis from the CRC Handbook of Chemistry and Physics 92nd Edition 2011-2013

Tantalum — (Gr. Tantalos, mythological character, father of Niobe), Ta; at. wt. 180.94788(2); at. no. 73; m.p. 3017 °C; b.p. 5458 °C; sp. gr. 16.4; valence 2?, 3, 4?, or 5. 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, Rwanda, Zimbabwe, Congo- Kinshasa, Nigeria, 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 that 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 a high index of refraction for camera lenses. The metal has many other uses. The price of (99.9%) tantalum is about $2/g.

Environmental Fate

Occurs almost invariably along with niobium. Found in the minerals columbite, tantalite & microlite. Obtained from ores tantalite or columbite mixed oxides of iton, manganese, niobium & tnatalum. Considered as rare element earth's crust contains about 0.003% of niobium & tantalum together.


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