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Jai Ganesh

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Technetium

Technetium

Gist

Technetium (Tc) is a chemical element with atomic number 43. It is a radioactive, silvery-grey metal, and the lightest element whose isotopes are all radioactive. Technetium is primarily known for its use in medical imaging, specifically as the radioactive isotope technetium-99m.

Technetium, specifically the isotope Technetium-99m (99mTc), is primarily used in medical imaging. It's the most common radioactive isotope tracer used in diagnostic procedures like Single-Photon Emission Computed Tomography (SPECT). 99mTc is used to image various parts of the body, including the brain, bones, lungs, kidneys, thyroid, heart, and more. Additionally, it's used in radiopharmaceuticals like Technetium Tc 99m oxidronate for bone imaging and Technetium 99m sestamibi for evaluating cardiac, breast, and parathyroid tissues.

Summary

Technetium is a chemical element; it has symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium and promethium are the only radioactive elements whose neighbours in the sense of atomic number are both stable. All available technetium is produced as a synthetic element. Naturally occurring technetium is a spontaneous fission product in uranium ore and thorium ore (the most common source), or the product of neutron capture in molybdenum ores. This silvery gray, crystalline transition metal lies between manganese and rhenium in group 7 of the periodic table, and its chemical properties are intermediate between those of both adjacent elements. The most common naturally occurring isotope is 99Tc, in traces only.

Many of technetium's properties had been predicted by Dmitri Mendeleev before it was discovered; Mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name ekamanganese (Em). In 1937, technetium became the first predominantly artificial element to be produced, hence its name (from the Greek technetos, 'artificial', + -ium).

One short-lived gamma ray–emitting nuclear isomer, technetium-99m, is used in nuclear medicine for a wide variety of tests, such as bone cancer diagnoses. The ground state of the nuclide technetium-99 is used as a gamma ray–free source of beta particles. Long-lived technetium isotopes produced commercially are byproducts of the fission of uranium-235 in nuclear reactors and are extracted from nuclear fuel rods. Because even the longest-lived isotope of technetium has a relatively short half-life (4.21 million years), the 1952 detection of technetium in red giants helped to prove that stars can produce heavier elements.

Details

Technetium (Tc) is a chemical element, synthetic radioactive metal of Group 7 (VIIb) of the periodic table, the first element to be artificially produced. The isotope technetium-97 (4,210,000-year half-life) was discovered (1937) by the Italian mineralogist Carlo Perrier and the Italian-born American physicist Emilio Segrè in a sample of molybdenum that had been bombarded by deuterons in the Berkeley (California) cyclotron. This isotope is the longest-lived member of a set from technetium-85 to technetium-114 that has since been produced. The most important isotope, because it is the only one available on a large scale, is technetium-99 (211,000-year half-life); it is produced in kilogram quantities as a fission product in nuclear reactors.

Technetium metal looks like platinum but is usually obtained as a gray powder. It crystallizes in the hexagonal close-packed structure and is a superconductor below 11.2 K. Except for technetium-99, technetium-97, and technetium-98 (4,200,000-year half-life), technetium isotopes are short-lived. The metastable isotope technetium-99m (6-hour half-life), used with radiographic scanning devices, is valuable for studying the anatomic structure of organs. Technetium is also used as a metallurgical tracer and in corrosion-resistant products.

Technetium occurs in the Earth’s crust as minute traces from the spontaneous fission of uranium; the relatively short half-lives preclude the existence of any primordial technetium on Earth. The American astronomer Paul W. Merrill’s discovery in 1952 that technetium-99 is present in S-type stars was a valuable piece of evidence concerning stellar evolution and nucleosynthesis. Technetium, chemically similar to rhenium (atomic number 75), exists in oxidation states of +7, +6, and +4 in compounds such as potassium pertechnetate, KTcO4, technetium chloride, TcCl6, and technetium sulfide, TcS2, respectively. Compounds are known in all formal oxidation states from -1 to +7.

Element Properties

atomic number  :  43
commonest isotope  :  (99)
melting point  :  2,172° C (3,942° F)
boiling point  :  4,877° C (8,811° F)
specific gravity  :  11.5 (20° C)
oxidation states  :  +4, +6, +7.

Additional Information:

Appearance

A radioactive, silvery metal that does not occur naturally.

Uses

The gamma-ray emitting technetium-99m (metastable) is widely used for medical diagnostic studies. Several chemical forms are used to image different parts of the body.

Technetium is a remarkable corrosion inhibitor for steel, and adding very small amounts can provide excellent protection. This use is limited to closed systems as technetium is radioactive.

Biological role

Technetium has no known biological role. It is toxic due to its radioactivity.

Natural abundance

The metal is produced in tonne quantities from the fission products of uranium nuclear fuel. It is obtained as a grey powder.

Early chemists puzzled over why they could not discover element number 43, but now we know why – its isotopes are relatively short-lived compared to the age of the Earth, so any technetium present when the Earth formed has long since decayed.

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