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Nobelium


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Atomic Number:102Atomic Symbol:No
Atomic Weight:259Electron Configuration:2-8-18-32-32-8-2
Shells:2,8,18,32,32,8,2Filling Orbital:5f14
Melting Point:oCBoiling Point:oC
Description:Man made radioactive metal.

History

(Alfred Nobel, discoverer of dynamite)
  • Nobelium was unambiguiously discovered and identified in April 1958 at Berkeley by A. Ghiorso, T. Sikkeland, J.R. Walton, and G.T. Seaborg, who used a new double-recoil technique.
  • A heavy-ion linear accelerator (HILAC) was used to bombard a thin target of curium (95% 244Cm and 4.5% 246Cm) with 12C ions to produce 102No according to the 246Cm(12C, 4n) reaction.
  • In 1957 workers in the United States, Britain, and Sweden announced the discovery of an isotope of element 102 with a 10-minute half-life at 8.5 MeV, as a result of bombarding 244Cm with 13C nuclei.
  • On the basis of this experiment, the name nobelium was assigned and accepted by the Commission on Atomic Weights of the International Union of Pure and Applied Chemistry.
  • The acceptance of the name was premature because both Russian and American efforts now completely rule out the possibility of any isotope of Element 102 having a half-life of 10 min in the vicinity of 8.5 MeV.
  • Early work in 1957 on the search for this element, in Russia at the Kurchatov Institute, was marred by the assignment of 8.9 +/- 0.4 MeV alpha radiation with a half-life of 2 to 40 sec, which was too indefinite to support discovery claims.
  • Confirmatory experiments at Berkeley in 1966 have shown the existence of 254-102 with a 55-s half-life, 252-102 with a 2.3-s half-life, and 257-102 with a 23-s half-life.
  • Following tradition giving the right to name an element to the discoverer(s), the Berkeley group in 1967, suggested that the hastily given name nobelium along with the symbol No , be retained.

Isotopes

Ten isotopes are now recognized, one of which -- 255-102 -- has a half-life of 3 minutes.

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