Tantalum

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	Tantalum

Notable Characteristics

Tantalum is gray, heavy, ductile, very hard, easily fabricated, highly resistant to corrosion by acids, and is a good conductor of heat and electricity. In fact, at temperatures below 150 °C tantalum is almost completely immune to chemical attack and can only be attacked by hydrofluoric acid[?], acidic solutions containing the fluoride ion, and free sulphur trioxide[?]. The element has a melting point exceeded only by tungsten and rhenium (melting point 3290 K, boiling point 5731 K).

Applications

The major use for tantalum, as tantalum metal powder, is in the production of electronic components, mainly tantalum capacitors. Major end uses for tantalum capacitors include portable telephones, pagers, personal computers, and automotive electronics.

Tantalum is also used to produce a variety of alloys that have high melting points, are strong and have good ductility. Alloyed with other metals, it is also used in making carbide tools for metalworking equipment and in the production of superalloys[?] for jet engine components, chemical process equipment, nuclear reactors, and missile parts. It is ductile and can be drawn into fine wire, which is used as a filament for evaporating metals such as aluminum.

Because it is totally immune to the action of body liquids and is nonirritating it is widely used in making surgical appliances. Tantalum oxide is to make special high index of refraction glass for camera lenses. The metal is also used to make vacuum furnace[?] parts.

History

Tantalum (Greek Tantalos, mythological character) was discovered in Sweden in 1802 by Anders Ekeberg[?] and isolated in 1820 by Jons Berzelius[?]. Many contemporary chemists believed niobium and tantalum were the same elements until 1844 and later 1866 when researchers showed that niobic and tantalic acids were different compounds. Early investigators were only able to isolate impure metal and the first relatively pure ductile metal was produced by Werner von Bolton[?] in 1903. Wires made with tantalum metal were used for light bulbs until tungsten replaced it.

Its name is derived from the character Tantalus, father of Niobe in Greek mythology, who was punished after death by being condemned to stand knee-deep in water with perfect fruit growing above his head, both of which eternally tantalized him - if he bent to drink the water, it drained below the level he could reach, and if he reached for the fruit, the branches moved out of his grasp. This was considered similar to tantalum's general non-reactivity - it sits among reagents and is unaffected by them.

Occurrence

Tantalum occurs principally in the mineral tantalite[?] [(Fe, Mn) Ta₂O₆] and euxenite (other minerals: samarskite[?], and fergusonite[?]).

Tantalum ores are mined in Australia, Brazil, Canada, the Democratic Republic of the Congo, Mozambique, Nigeria, Portugal, and Thailand.

Tantalite is largely found mixed with columbite in an ore called coltan, about whose sources ethical questions have been raised (see the article).

Several complicated steps are involved in the separation of tantalum from niobium. Commercially production of this element can follow one of several different methods which includes; electrolysis of molten potassium fluorotantalate, reduction of potassium fluorotantalate with sodium, or by reacting tantalum carbide with tantalum oxide. Tantalum is also a byproduct from tin extraction.

Compounds

Los Alamos National Laboratory scientists have made a tantalum carbide graphite composite[?] material that is one of the hardest materials made.

Isotopes

Natural tantalum consists of two isotopes. Ta-181 is a stable isotope, and Ta-180 is a radioactive isotope that quickly transforms into a nuclear isomer with a half life of over a 10¹⁵[?] years (1 with 15 zeros).

Precautions

Tantalum containing compounds are rarely encountered, and the metal doesn't normally cause problems in the laboratory, but it should still be regarded as highly toxic. There is some evidence that tantalum compounds can cause tumors, and its metal dust is a fire and explosion hazard.

External Links

WebElements.com - Tantalum (http://www.webelements.com/webelements/elements/text/Ta/index.html)
EnvironmentalChemistry.com - Tantalum (http://environmentalchemistry.com/yogi/periodic/Ta.html)

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