 |
|
ESSAY SAMPLE ON "HISTORY, PROPERTIES AND USES OF TECHNETIUM" |
TECHNETIUM
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 d
iscovery,
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 fou
nd in the
spectrum of S-, M-, and N-type stars, and its resence in stellar matter i
s leading to
new theories of the production of heavy elements in the stars. Nineteen i
sotopes of
technetium, with atomic masses ranging from 90 to 108, are known. 97Tc ha
s a half-life of 2.6 x 10^6 years. 98Tc has a half-life of 4.2 x 10^6 years. The isomer
ic isotope
95mTc, with a half-life of 61 days, is useful for tracer work, as it prod
uces energetic
gamma rays. Technetium metal has been produced in kilogram quantities. Th
e 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. Technet
ium dissolves in
nitric acid, aqua regia, and conc. sulfuric acid, but is not soluble in h
ydrochloric 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 prote
ction is
limited to closed systems, since technetium is radioative and must be con
fined. 98Tc
has a specific activity of 6.2 x 10^8 Bq/g. Activity of this level must n
ot be allowed to
spread. 99Tc is a contamination hazard and should be handled in a glove b
ox. The metal
is an excellent superconductor at 11K and below.
Source: CRC Handbook of Chemistry and Physics, 1913-1995. David R. Lide, Editor
in Chief. Author:
C.R. Hammond
|
| Click here for more essays on HISTORY, PROPERTIES AND USES OF TECHNETIUM |
|
|
|