7440-26-8 Usage
Description
Technetium is a radioactive metallic transition element with the symbol Tc and atomic number 43. It is a member of group VIIB in the periodic table and has valences of 4, 5, 6, and 7. Technetium does not occur naturally on Earth and is artificially produced by bombarding molybdenum with neutrons or during the fission of uranium. It has a silver-gray appearance, a melting point of 2,172°C, a boiling point of 4,877°C, and a density of 11.50 g/cm3. Technetium and its alloys are superconductors and can be used to create high-strength magnetic fields at low temperatures.
Uses
1. Used in Metallurgical Industry:
Technetium is used as a metallurgical tracer for tracking the flow of metals in industrial processes and as an alloy metal to produce super-strong magnets that are supercooled to near absolute zero to improve their efficiency.
2. Used in Cryochemistry:
Technetium is used as an alloy metal to create super-strong magnets that are supercooled, which are used in imaging equipment and potentially in future magnetic-driven trains.
3. Used in Corrosion Resistance:
Technetium is used as an alloy metal to create corrosion-resistant alloy metals. A very small amount (55-ppm) added to iron creates a corrosion-resistant alloy metal.
4. Used in Nuclear Medicine:
A radioisotope of technetium, Tc-99m, is widely used in nuclear medicine. The patient is injected with saline solution containing Tc-99m, which emits energy in the form of very penetrating gamma rays. This energy is used to expose an X-ray film that depicts the internal image of the organ under examination. The procedure is safe due to Tc-99m's short half-life of 6.015 hours.
5. Used in Pipelines:
Technetium's radioactivity makes it useful as a tracer in the production of metals and tracing flowing fluids in pipelines.
Isotopes
There are 47 isotopes. None are stable and all are radioactive. Most are producedartificially in cyclotrons (particle accelerators) and nuclear reactors. The atomicmass of its isotopes ranges from Tc-85 to Tc-118. Most of technetium’s radioactiveisotopes have very short half-lives. The two natural radioisotopes with the longest halflives—Tc-98 = 4.2×10+6 years and Tc-99 = 2.111×10+5 years—are used to establishtechnetium’s atomic weight.
Origin of Name
Technetium’s name was derived from the Greek word technetos,
meaning “artificial.”
Characteristics
Technetium was the first element, not found on Earth, to be artificially produced by bombardingmolybdenum with deuterons.The major characteristic of technetium is that it is the only element within the 29 transitionmetal-to-nonmetal elements that is artificially produced as a uranium-fission product innuclear power plants. It is also the lightest (in atomic weight) of all elements with no stableisotopes. Since all of technetium’s isotopes emit harmful radiation, they are stored for sometime before being processed by solvent extraction and ion-exchange techniques. The two longlivedradioactive isotopes, Tc-98 and Tc-99, are relatively safe to handle in a well-equippedlaboratory.Since all of technetium’s isotopes are produced artificially, the element’s atomic weight(atomic mass units) is determined by which isotopes are selected for the calculation.
History
Element 43 was predicted on the basis of the
periodic table, and was erroneously reported as having been
discovered in 1925, at which time it was named masurium.
Technetium was actually discovered by Perrier and Segre in
Italy in 1937. It was found in a sample of molybdenum that
was bombarded by deuterons 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 materials have
been made without success. 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 presence in
stellar matter is leading to new theories of the production of
heavy elements in the stars. Forty-three isotopes and isomers
of technetium, with mass numbers ranging from 86 to 113,
are known. 97Tc has a half-life of 2.6 × 106 years. Tc has a
half-life of 4.2 × 106 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 1100°C over Tc2S7. It is now conveniently
prepared by the reduction of ammonium pertechnetate with
hydrogen. Technetium is a silvery-gray metal that tarnishes
slowly in moist air. Until 1960, technetium was available only
in small amounts and the price was as high as $2800/g, but
the price is now of the order of $100/g. The chemistry of technetium
is similar to that of rhenium. Technetium dissolves in
nitric acid, aqua regia, and concentrated sulfuric acid, but is
not soluble in hydrochloric acid of any strength. The element
is a remarkable corrosion inhibitor for steel. It is reported that mild carbon steels may be effectively protected by as little as
55 ppm of KTcO4 in aerated distilled water at temperatures up
to 250°C. This corrosion protection is limited to closed systems,
since technetium is radioactive and must be confined.
99Tc has a specific activity of 6.2 × 108 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.
Preparation
Technetium isotopes are prepared by bombardment of molybdenum with protons and neutrons. A few nuclear reactions are shown for the three longlived isotopes:
Technetium-99 also is a fission product of uranium-235.
Pure technetium metal may be prepared by reducing ammonium pertechnate, NH4TcO4, with hydrogen at high temperatures. Hydrogen reduction at about 200°C first forms the oxide, TcO2, which is reduced to Tc metal at 600 to 800°C.
Hazard
The hazards of technetium are the same as for all radioactive elements. Excessive exposureto radiation can cause many kinds of tissue damage—from sunburn to radiation poisoningto death.
Check Digit Verification of cas no
The CAS Registry Mumber 7440-26-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 7,4,4 and 0 respectively; the second part has 2 digits, 2 and 6 respectively.
Calculate Digit Verification of CAS Registry Number 7440-26:
(6*7)+(5*4)+(4*4)+(3*0)+(2*2)+(1*6)=88
88 % 10 = 8
So 7440-26-8 is a valid CAS Registry Number.
InChI:InChI=1/Tc
