Nobelium

melting point: Unknown
boiling point: Unknown
density: Unknown
most common ions: No ²⁺, No ³⁺

The first claim for the discovery of the element nobelium was made in Sweden in 1957. However, neither American nor Soviet researchers could duplicate the original results, which are now known to have been interpreted incorrectly. The actual discovery of nobelium is credited to researchers in Berkeley, California, who in 1958 bombarded a curium target (95% ²⁴⁴Cm and 4.5% ²⁴⁶Cm) plated on a nickel foil with 60 to 100 MeV ¹²C ions, and detected both the 8.4 MeV α -particles created by the radioactive decay of ²⁵²No and the ²⁵⁰Fm created from the α -decay of ²⁵⁴No. Known isotopes of nobelium possess 148 to 160 neutrons and 102 protons; all are radioactive, with half-lives ranging between 2.5 milliseconds and 58 minutes, and decay by spontaneous fission , α -particle emission, or electron capture. ²⁵⁹No has the longest half-life: 58 minutes.

Nobelium is a member of the actinide series of elements. The ground state electron configuration is assumed to be (Rn)5f147s2, by analogy with the equivalent lanthanide element ytterbium ([Kr]4f146s2); there has never been enough nobelium made to experimentally verify the electronic configuration. Unlike the other actinide elements and the lanthanide elements, nobelium is most stable in solution as the dipositive cation No²⁺. Consequently its chemistry resembles that of the much less chemically stable dipositive lanthanide cations or the common chemistry of the alkaline earth elements. When oxidized to No³⁺, nobelium follows the well-established chemistry of the stable, tripositive rare earth elements and of the other tripositive actinide elements (e.g., americium and curium).

see also Actinium; Berkelium; Einsteinium; Fermium; Lawrencium; Mendelevium; Neptunium; Plutonium; Protactinium; Rutherfordium; Thorium; Uranium.

Mark Jensen

Bibliography

Hoffman, Darleane C.; Ghiorso, Albert; and Seaborg, Glenn Theodore (2000). The Transuranium People: The Inside Story. London: Imperial College Press.

nobelium , artificially produced radioactive chemical element; symbol No; at. no. 102; mass no. of most stable isotope 259; m.p. 827°C; b.p. and density unknown; valence +2, +3. It is a metal of the actinide series in Group 3 of the periodic table . Nobelium was the 10th transuranium element to be discovered. It was first produced and detected in Apr., 1958, by Albert Ghiorso, Torbjørn Sikkeland, John R. Walton, and Glenn T. Seaborg at the Univ. of California at Berkeley; they used a heavy-ion linear accelerator to bombard a mixture of curium-244 and curium-246 with carbon-12 ions, producing nobelium-254 ( half-life 55 sec). The name of the element was originally suggested by scientists at the Nobel Institute of Physics, who in 1957 reported synthesis of an isotope of the element; although the name was adopted, it was later shown that the element could not have the properties they reported. Thirteen isotopes, all of which are radioactive, are known; the most stable, nobelium-259, has a 58-min half-life.

nobelium (symbol No) Radioactive metallic element, one of the actinide series of elements. Seven isotopes are known. It was discovered in 1958 by US nuclear scientist Albert Ghiorso (1915– ) and colleagues at the Lawrence Radiation laboratory in Berkeley, California. Properties: at.no. 102, most stable isotope No²⁵⁵ (half-life 3 minutes). See also transuranic elements

no·bel·i·um / nōˈbelēəm/ • n. the chemical element of atomic number 102, a radioactive metal of the actinide series. Nobelium does not occur naturally and was first produced by bombarding curium with carbon nuclei. (Symbol: No)

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