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Chemical Fact Sheet

Nobelium

Chemical Abstract Number (CAS #) 10028-14-5
Analytical Methods 200.8 - 6020
Atomic Symbol No

Synopsis from the CRC Handbook of Chemistry and Physics 92nd Edition 2011-2013

Nobelium — (Alfred Nobel [1833–1896], inventor of dynamite), No; at. wt. [259]; at. no. 102; valence +2, +3. Nobelium was unambiguously 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 102254 according to the 246Cm (12C, 4n) reaction. Earlier in 1957 workers of the U.S., Britain, and Sweden announced the discovery of an isotope of Element 102 with a 10-min 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, for 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 halflife of 2 to 40 sec, which was too indefinite to support claim to discovery. Confirmatory experiments at Berkeley in 1966 have shown the existence of 254102 with a 55-s half-life, 252102 with a 2.3-s half-life, and 257102 with a 25-s half-life. Twelve isotopes are now recognized, one of which — 255102 — has a half-life of 3.1 min. In view of the discoverer’s traditional right to name an element, the Berkeley group, in 1967, suggested that the hastily given name nobelium, along with the symbol No, be retained.


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