Paper due 02/07/97
Atomic Number: 43
Atomic Symbol: Tc
Atomic Weight: (97)
Electron Configuration: -18-13-2
History, Properties and Uses:
(Gr. technetos, artificial) Element 43 was predicted on the basis of the
periodi 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 erons 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 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 its
resence 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. 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 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 1100C over Tc2S7. It is now
conveniently prepared by the reduction of ammonium pertechnetate with hydrogen.
Techne tium is a silvery-gray metal that tarnishes slowly in moist air. Until
1960, techne tium 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.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 250C. This
corrrosion protection is limited to closed systems, since technetium is
radioative 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 contamination
hazard and should be handled in a glove box. The metal is an excellent
superconductor at 11K and below.
CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor
in Chief. Author: C.R. Hammond