Technetium Nalin BalanNUCL 200 Paper due 02/07/97 Atomic Number: 43 Atomic Symbol: Tc Atomic Weight: (97) Electron Configuration: -18-13-2 History, Properties and Uses: (Gr. , artificial) Element 43 was predicted on the basis of c table, and was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by Perrier and Segre in Italy in 1937. It was found in a sample of molybdenum, which was bombarded by deut er ons in the Berkeley cyclotron, and which E. Lawrence sent to these investigators. Technetium was the first element to be produced artificially.
Since its discovery, searches for the element in terrestrial material have been made without s uc cess. If it does exist, the concentration must be very small. Technetium has been found in the spectrum of S-, M-, and N-type stars, and in stellar matter is leading to new theories of the production of heavy elements in the stars. Nineteen isotopes of technetium, with atomic masses ranging from 90 to 108, are known. 97 Tc has a half-life of 2. 6 x 10^6 years.
98 Tc has a half-life of 4. 2 x 10^6 years. The isomeric isotope 95 mTc, with a half-life of 61 days, is useful for tracer work, as it produces energetic gamma rays. Technetium metal has been produced in kilogram quantities. The metal was first prepared by passing hydrogen gas at 1100 C over Tc 2 S 7.
It is now conveniently prepared by the reduction of ammonium with hydrogen. Techn e tiu m is a silvery-gray metal that tarnishes slowly in moist air. Until 1960, tech ne tiu m was available only in small amounts and the price was as high as $2800/g. It is now commercially available to holders of O. R. N.
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L. permits at a price of $60/g. The chemistry of technetium is said to be similar to that of rhenium. Technetium dissolves in nitric acid, aqua regia, and conc.
sulfuric acid, but is not soluble in hydrochloric acid of any strength. The element is a remarkable corrosion inhibitor for steel. It is reported aerated distilled water at temperatures up to 250 C. Thiscorrrosion protection is limited to closed systems, since technetium and must be confined.
98 Tc has a specific activity of 6. 2 x 10^8 Bq / g . Activity of this level must not be allowed to spread. 99 Tc is a contamination hazard and should be handled in a glove box. The metal is an excellent superconductor at 11 K and below. Source: CRC Handbook of Chemistry and Physics, 1913-1995.
David R. Lide, Editor in Chief. Author: C. R. Hammond.
