technetium

/tek nee"shee euhm, -sheuhm/, n.
Chem. an element of the manganese family, not found in nature, but obtained in the fission of uranium or by the bombardment of molybdenum. Symbol: Tc; at. wt.: 99; at. no.: 43; sp. gr.: 11.5.
[1945-50; < Gk technet(ós) artificial (lit., made, verbid of technâsthai; see TECHNO-) + -IUM]

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Metallic chemical element, one of the transition elements, chemical symbol Tc, atomic number 43.

All its isotopes are radioactive (see radioactivity); some occur in trace amounts in nature as nuclear fission products of uranium. Its isotope technetium-97 was the first element artificially produced (1937; see cyclotron). Technetium-99, a fission product of nuclear reactors that emits gamma rays, is the most-used tracer isotope in nuclear medicine. Technetium resembles platinum in appearance and manganese and rhenium in chemical behaviour. It is also used as a metallurgical tracer and in corrosion-resistant products.

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 chemical element, synthetic radioactive metal of Group 7 (VIIb) of the periodic table, the first element to be artificially produced. The isotope technetium-97 (2,600,000-year half-life) was discovered (1937) by the Italian mineralogist Carlo Perrier and the Italian-born American physicist Emilio Segrè (Segrè, Emilio) 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-92 to technetium-107 that has since been produced. The most important isotope, because it is the only one available on a large scale, is technetium-99 (212,000-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 (1,500,000-year half-life), technetium isotopes are short-lived. Technetium has essentially no uses.

      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.

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
electronic config.
[Kr]4d65s1

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Universalium. 2010.

Look at other dictionaries:

  • Technetium — Technétium Technétium Molyb …   Wikipédia en Français

  • Technétium — Molybdène ← Technétium → Ruthénium Mn …   Wikipédia en Français

  • Technetium-99 — (99Tc) is an isotope of technetium which decays with a half life of 211,000 years, emitting soft beta rays but no gamma rays, and has a fission product yield of 6.0507% for thermal neutron fission of uranium 235. It is the most significant long… …   Wikipedia

  • TECHNÉTIUM — Du grec tekhnétos , artificiel. Symbole chimique: Tc Numéro atomique: 43 Masse atomique: 98,9 g Point de fusion: 2 172 0C Point d’ébullition: 4 877 0C Densité (à 20 0C): 11,5 Métal du groupe du manganèse produit artificiellement pour la première… …   Encyclopédie Universelle

  • technetium — Symbol: Tc Atomic number: 43 Atomic weight: (98) Radioactive metallic transition element. Can be detected in some stars and the fission products of uranium. First made by Perrier and Segre by bombarding molybdenum with deutrons, giving them Tc 97 …   Elements of periodic system

  • technetium — [tek nē′shē əm, tek nē′shəm] n. [ModL < Gr technētos, artificial (< technasthai, to contrive by art < technē: see TECHNIC) + IUM: so named (1947) by E. G. Segré (1905 89), It American physicist, and C. Perrier, It physicist, who… …   English World dictionary

  • Technetium — molybdenum ← technetium → ruthenium Mn ↑ Tc ↓ Re …   Wikipedia

  • Technetium — Eigenschaften …   Deutsch Wikipedia

  • Technétium 99 — Le technétium 99, noté 99Tc, est l isotope du technétium dont le nombre de masse est égal à 99 : son noyau atomique compte 43 protons et 56 neutrons avec un spin 9/2+ pour une masse atomique de 98,9062547 g/mol. Il est caractérisé par… …   Wikipédia en Français

  • Technetium — Tc (Symbol) * * * Tech|ne|ti|um 〈n.; s; unz.; chem. 〉 künstlich hergestelltes, radioaktives chemisches Element, Ordnungszahl 43 [<grch. technetos „künstlich“] * * * Tech|ne|ti|um [griech. techne̅tós = künstlich gemacht (téchne̅ = Kunst,… …   Universal-Lexikon

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