Nobelium
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| Name, Symbol, Number | Nobelium, No, 102 | ||||||||||||||||||||||||
| Chemical series | Actinides | ||||||||||||||||||||||||
| Period, Block | 7, f | ||||||||||||||||||||||||
| Appearance | unknown | ||||||||||||||||||||||||
| Atomic weight | [259] u | ||||||||||||||||||||||||
| Electron configuration | [Rn] 5f14 7s2 | ||||||||||||||||||||||||
| e- 's per energy level | 2, 8, 18, 32, 32, 8, 2 | ||||||||||||||||||||||||
| State of matter | Presumably a solid | ||||||||||||||||||||||||
| Most stable isotopes | |||||||||||||||||||||||||
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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 1958.
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Notable characteristics
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, nobelium-259, has a half-life of 58 minutes and decays to fermium-255 through alpha decay or to mendelevium-259 through electron capture.
History
Nobelium (named for Alfred Nobel) was first synthesized by Albert Ghiorso, Glenn T. Seaborg, John R. Walton and Torbj?ikkeland 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% Cm-244 and 4.5% Cm-246) with carbon-12 ions to make nobelium-254 (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 curium-244 with carbon-13 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 nobelium-254 (half-life 55 s), nobelium-252 (half-life 2.3 s), and nobelium-257 (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
13 radioisotopes of nobelium have been characterized, with the most stable being No-259 with a half-life of 58 minutes, No-255 with a half-life of 3.1 minutes, and No-253 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, No-254m (t? 0.28 seconds).
The known isotopes of nobelium range in atomic weight from 249.088 u (No-249) to 262.108 u (No-262). The primary decay mode before the most stable isotope, No-259, is alpha emission, and the primary mode after is spontaneous fission. The primary decay products before No-259 are element 100 (fermium) isotopes, and the primary products after are energy and subatomic particles.
References
- Los Alamos National Laboratory - Nobelium (http://periodic.lanl.gov/elements/102.html)
- Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
- It's Elemental - Nobelium (http://education.jlab.org/itselemental/ele102.html)
External links
- WebElements.com - Nobelium (http://www.webelements.com/webelements/elements/text/No/index.html)
- EnvironmentalChemistry.com - Nobelium (http://environmentalchemistry.com/yogi/periodic/No.html)