Technetium similar to that of rhenium. Technetium dissolves

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TechnetiumNalin BalanNUCL 200Paper due 02/07/97Atomic Number: 43Atomic Symbol: TcAtomic Weight: (97)Electron Configuration: -18-13-2History, Properties and Uses:(Gr. technetos, artificial) Element 43 was predicted on the basis of theperiodi c table, and was erroneously reported as having been discovered in 1925,at which time it was named masurium. The element was actually discovered byPerrier and Segre in Italy in 1937.

It was found in a sample of molybdenum,which was bombarded by deut erons in the Berkeley cyclotron, and which E.Lawrence sent to these investigators.Technetium was the first element to be produced artificially.

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Since itsdiscovery, searches for the element in terrestrial material have been madewithout s uccess. 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 itsresence in stellar matter is leading to new theories of the production of heavyelements in the stars. Nineteen isotopes of technetium, with atomic massesranging from 90 to 108, are known. 97Tc has a half-life of 2.6 x 10^6 years.

98Tc has a half-life of 4.2 x 10^6 years. The isomeric isotope 95mTc, with ahalf-life of 61 days, is useful for tracer work, as it produces energeticgamma rays. Technetium metal has been produced in kilogram quantities.

The metalwas first prepared by passing hydrogen gas at 1100C over Tc2S7. It is nowconveniently prepared by the reduction of ammonium pertechnetate with hydrogen.Techne tium is a silvery-gray metal that tarnishes slowly in moist air. Until1960, techne tium was available only in small amounts and the price was as highas $2800/g. It is now commercially available to holders of O.R.N.L.

permits at aprice of $60/g. The chemistry of technetium is said to be similar to that ofrhenium. Technetium dissolves in nitric acid, aqua regia, and conc. sulfuricacid, but is not soluble in hydrochloric acid of any strength. The element is aremarkable corrosion inhibitor for steel.

It is reported aerated distilled water at temperatures up to 250C. Thiscorrrosion protection is limited to closed systems, since technetium isradioative and must be confined. 98Tc has a specific activity of 6.2 x 10^8 Bq/g.Activity of this level must not be allowed to spread.

99Tc is a contaminationhazard and should be handled in a glove box. The metal is an excellentsuperconductor at 11K and below.Source:CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editorin Chief.

Author: C.R. Hammond


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