| Atomic Number: |
102 |
| Atomic Symbol: |
No |
| Atomic Weight: |
259 |
| Electron Configuration: |
[Rn]7s25f14 |
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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