|Name, Symbol, Number||nobelium, No, 102|
|Group, Period, Block||n/a, 7, f|
|Appearance||unknown, probably silvery
white or metallic gray
|Atomic mass||(259) g/mol|
|Electron configuration||[Rn] 5f14 7s2|
|Electrons per shell||2, 8, 18, 32, 32, 8, 2|
|Melting point||1100 K
(827 °C, 1521 °F)
|Oxidation states||2, 3|
|Electronegativity||1.3 (Pauling scale)|
|Ionization energies||1st: 642 kJ/mol|
|CAS registry number||10028-14-5|
Nobelium (chemical symbol No, atomic number 102), also known as unnilbium (symbol Unb), is a synthetic element in the periodic table. A radioactive metallic transuranic element in the actinide series, it is synthesized by bombarding curium with carbon ions. It was first identified by a team led by Albert Ghiorso and Glenn T. Seaborg in 1957. It is of interest mainly for research purposes, and no practical applications have yet been developed.
Nobelium (named for Alfred Nobel) was first synthesized by Albert Ghiorso, Glenn T. Seaborg, John R. Walton and Torbjørn Sikkeland in April 1958 at the University of California, Berkeley. The team used the new heavy-ion linear accelerator (HILAC) to bombard a curium target (95 percent 244Cm and 4.5 percent 246Cm) with 12C ions to make 254No (half-life 55 seconds). Their work was confirmed by Soviet researchers in Dubna.
A year earlier, however, physicists at the Nobel Institute in Sweden announced that they had synthesized an isotope of element 102. The team reported that they created an isotope with a half-life of 10 minutes at 8.5 MeV after bombarding 244Cm with 13C nuclei. Based on this report, the Commission on Atomic Weights of the International Union of Pure and Applied Chemistry assigned and accepted the name nobelium and the symbol No for the "new" element. Subsequent Russian and American efforts to repeat the experiment failed.
In 1966, researchers at UC Berkeley confirmed the 1958 experiments and went on to show the existence of 254No (half-life 55 s), 252No (half-life 2.3 s), and 257No (half-life 23 s). The next year Ghiorso's group decided to retain the name "nobelium" for element 102.
Nobelium was the most recent element "of which the news had come to Harvard" when Tom Lehrer wrote "The Elements Song" and was therefore the element with the highest atomic number to be included.
Nobelium is an inner transition metal of the actinide series, located in period 7 of the periodic table, between mendelevium and lawrencium. Little is known about nobelium and only small quantities of it have ever been produced. Its most stable isotope, 259No, has a half-life of 58 minutes and decays to 255Fm through alpha decay or to 259Md through electron capture.
Thirteen radioisotopes of nobelium have been characterized, with the most stable being 259No with a half-life of 58 minutes, 255No with a half-life of 3.1 minutes, and 253No with a half-life of 1.7 minutes. All of the remaining radioactive isotopes have half-lives that are less than 56 seconds, and all of these have half-lives that are less than 2.4 seconds. This element also has 1 meta state, 254mNo (t½ 0.28 seconds).
The known isotopes of nobelium range in atomic weight from 249.088 u (249No) to 262.108 u (262No). The primary decay mode before the most stable isotope, 259No, is alpha emission, and the primary mode after is spontaneous fission. The primary decay products before 259No are element 100 (fermium) isotopes, and the primary products after are energy and subatomic particles.
All links retrieved January 21, 2015.
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