Title: Technetium
CAS Registry Number: 7440-26-8
Literature References: Tc; at. no. 43. Usual valences 4 and 7; 3 less common. Group VIIB (7). Radioactive element; no stable nuclides. Discovery claimed by Noddack, Tacke, and Berg who called it "masurium"; the existence of masurium has never been confirmed by isoln of the element. First artificially produced element. Named from the Greek word for "artificial"; separated from a molybdenum plate that had been bombarded for a few months with a strong beam of deuterons in the Berkeley cyclotron: Perrier, Segré, Nature 140, 193 (1937); eidem, J. Chem. Phys. 5, 712 (1937); Cacciapuoti, Segré, Phys. Rev. 52, 1252 (1937). Most commonly available isotope (mass number): 99 (T½ 2.12´105 years, rel. at. mass 98.9063). Other long-lived isotopes: 97 (T½ 2.6´106 years, rel. at. mass 96.9064); 98 (T½ 4.2´106 years, longest-lived isotope, rel. at. mass 97.9072). Known artificial isotopes: 92-107. Prepn of metal: Cobble et al., J. Am. Chem. Soc. 74, 1852 (1952). Comprehensive reviews: Boyd, J. Chem. Educ. 36, 3-14 (1959); Schwochau, Angew. Chem. 76, 9-19 (1964); Kotegov et al., in Adv. Inorg. Chem. Radiochem. 11, 1-90 (1968); Peacock in Comprehensive Inorganic Chemistry vol. 3, J. C. Bailar Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 877-903. Pharmacokinetics and organ distribution of radiopharmaceuticals: O. P. D. Noronha, K. S. Venkateswarlu, Eur. J. Nucl. Med. 6, 121 (1980).
Properties: Close-packed hexagonal structure; isomorphous with rhodium, ruthenium, and osmium. The element obtained by hydrogen reduction of ammonium pertechnate is a silver-gray spongy mass which tarnishes slowly in moist air. mp 2250 ±50°. In its chemical behavior resembles rhenium. The element is precipitated by hydrogen sulfide from hydrochloric acid (diluted up to 5N); for higher acid concns the precipitation is not complete. Is oxidized by hydrogen peroxide in alkaline soln into sol anions: Perrier, Segré, Atti R. Accad. Lincei [6] 27, 579 (1938); Segré, Nature 143, 460 (1939). Reacts with dil or concd nitric acid, in aqua regia, in concd sulfuric acid; not with HCl. Burns in fluorine to form penta- and hexafluorides. Combines with sulfur at high temp to form disulfide; with carbon to form TcC.
Melting point: mp 2250 ±50°
Use: Minute quantities of TcO4- ion exert remarkable inhibition of the corrosion of soft iron in neutral aq soln: Cartledge, J. Am. Chem. Soc. 77, 2658 (1955).
Therap-Cat: 99mTc as diagnostic aid (radioactive imaging agent).
Keywords: Diagnostic Aid (Radioactive Imaging Agent).

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