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Nobelium - No

CAS: 10028-14-5
Description: Radioactive metal
Classification: Actinide / Transuranium
Date of Discovery: 1957
Discoverer: Nobel Institute for Physics
Name Origin: Alfred Nobel, discoverer of dynamite

Atomic Number: 102
Number of Neutrons: 157
Atomic Mass: (259) amu
Melting Point: 827 C (?)
Boiling Point:
Density (293 K):
Atomic volume:
Electrical resistivity:
Thermal conductivity: 0.1 W/cmK
Enthalpy of atomization:
Enthalpy of vaporization:
Enthalpy of fusion:
Specific heat capacity:
Energy levels: 2-8-18-32-32-8-2
Electron configuration: [Rn]5f 147s2
Crystal Structure:
Atomic radius:
Covalent radius:
Oxidation States: +2, +3
Electronegativity, Pauling: 1.3
Electron affinity:
First ionization energy: 6.65 eV
2nd ionization energy:
3rd ionization energy:
Polarizability: 17.5 10-24cm3
Isotope Atomic Mass Half-life Decay Mode Spin
250No 0.25 ms SF 0+
251No 251.0889 0.8 s alpha symbol
252No 252.08897 2.3 s alpha symbol; SF 0+
253No 253.0907 1.7 m alpha symbol; EC (9/2-)
254mNo 0.28 s IT
254No 254.09095 55 s alpha symbol; EC
255No 255.09323 3.1 m alpha symbol; EC 1/2+
256No 256.09428 2.9 s alpha symbol 0+
257No 257.09685 25 s alpha symbol (7/2+)
258No 258.0983 Alpha Symbol1.2 ms SF 0+
259No 259.1011 58 m alpha symbol; EC (9/2+)
262No 262.108 Alpha Symbol8 ms SF
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 254102 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 half-life 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-sec half-life, 252102 with a 2.3-sec half-life, and 257102 with a 25-sec half-life. Twelve isotopes are now recognized, one of which (255102) has a half-life of 3.l min. In view of the discover'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.
LINKS:

Gammasphere leads explorers along the rim of the valley of nuclear stability
A New Spin on Nobelium
Glenn Seaborg - Scientific Work
Spectroscopy of 254-Nobelium


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Sources for the information on this website include:
Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.