Nobelium

2007 Schools Wikipedia Selection. Related subjects: Chemical elements

102 mendelevium ← nobelium → lawrencium Yb ↑ No ↓ (Upb) Periodic Table - Extended Periodic Table
General
Name, Symbol, Number	nobelium, No, 102
Chemical series	actinides
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
Physical properties
Phase	solid
Melting point	1100  K (827 ° C, 1521 ° F)
Atomic properties
Electronegativity	1.3 (Pauling scale)
Ionization energies	1st: 642 kJ/mol
Miscellaneous
CAS registry number	10028-14-5
Selected isotopes
Main article: Isotopes of nobelium iso NA half-life DM DE ( MeV) DP 253No syn 1.7 m α 8.440 249Fm ε 3.200 253Md 255No syn 3.1 m α 8.445 251Fm ε 2.012 255Md 259No syn 58 m α 7.910 255Fm ε 0.500 259Md SF - -
References

Nobelium ( IPA: /ˌnə(ʊ)ˈbiːliəm/), also known as unnilbium ( IPA: /ˌjuːˈnɪlbiəm/, symbol Unb), 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.

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, ²⁵⁹No, has a half-life of 58 minutes and decays to ²⁵⁵Fm through alpha decay or to ²⁵⁹Md through electron capture.

History

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

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.