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Tantalum halides span the oxidation states of +5, +4, and +3. Tantalum pentafluoride (TaF 5) is a white solid with a melting point of 97.0 °C. The anion [TaF 7] 2-is used for its separation from niobium. [41] The chloride TaCl 5, which exists as a dimer, is the main reagent in synthesis of new Ta compounds. It hydrolyzes readily to an oxychloride.
Natural tantalum (73 Ta) consists of two stable isotopes: 181 Ta (99.988%) and 180m Ta (0.012%). There are also 35 known artificial radioisotopes, the longest-lived of which are 179 Ta with a half-life of 1.82 years, 182 Ta with a half-life of 114.43 days, 183 Ta with a half-life of 5.1 days, and 177 Ta with a half-life of 56.56 hours.
The mineral group tantalite [(Fe, Mn)Ta 2 O 6] is the primary source of the chemical element tantalum, a corrosion (heat and acid) resistant metal. It is chemically similar to columbite , and the two are often grouped together as a semi-singular mineral called coltan or "columbite-tantalite" in many mineral guides.
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For example, TaC has a microhardness of 1,600–2,000 kg/mm 2 [18] (~9 Mohs) and an elastic modulus of 285 GPa, whereas the corresponding values for tantalum are 110 kg/mm 2 and 186 GPa. [19] Tantalum carbides have metallic electrical conductivity, both in terms of its magnitude and temperature dependence. TaC is a superconductor with a ...
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Tetravalent VOSO 4 has been reported to be at least 5 times more toxic than trivalent V 2 O 3. [103] The Occupational Safety and Health Administration has set an exposure limit of 0.05 mg/m 3 for vanadium pentoxide dust and 0.1 mg/m 3 for vanadium pentoxide fumes in workplace air for an 8-hour workday, 40-hour work week. [104]