Nobelium, also known as unnilbium, is a synthetic element in the periodic table that has the symbol No and atomic number 102. A radioactive metallic transuranic element in the actinide series, nobelium is synthesized by bombarding curium with carbon ions. It was first identified by a team led by Albert Ghiorso and Glenn T. Seaborg in 1958C&EN: It’s Elemental: The Periodic Table - Nobelium , webpage, retrieved June 18, 2006.

Notable characteristics

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Little is known about nobelium and only small quantities of it have ever been produced. It has no uses whatsoever outside of the laboratory. 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.

History

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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% ²⁴⁴Cm and 4.5% 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.

Isotopes

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13 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-lifes that are less than 56 seconds, and all of these have half lifes that are less than 2.4 seconds. This element also has 1 meta state, ^254mNo (t_½ 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.

References

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• Los Alamos National Laboratory - Nobelium
• Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
• It's Elemental - Nobelium

External links

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• WebElements.com - Nobelium

Actinides | Chemical elements

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