Nobelium (102)

Nobelium is a radioactive "rare earth metal" named after Alfred Nobel who discovered dynamite. Little is known about the element but limited chemical experiments have shown that it forms a stable divalent ion in solution as well as the predicted trivalent ion that is associated with its presence as one of the actinides.

Name: Nobelium Symbol: No Atomic number: 102 Atomic weight: [ 259 ] Standard state: presumably a solid at 298 K CAS Registry ID: 10028-14-5 Group Name: Actinoid Period in Periodic Table: 7 (actinoid) Block in Periodic Table: f-block Color: Unknown, but probably metallic and silvery white, or grey Classification: Metallic

Historical information

Nobelium was discovered by Nobel Institute for Physics in Sweden, 1957 and later (1958) by Seaborg and others at Berkeley, California. Element was named after Alfred "Nobel", Swedish chemist who discovered dynamite, and founder of the Nobel Prizes. Element 102 was first named nobelium (No) by its claimed discoverers in 1957 by scientists at the Nobel Institute in Sweden. The name was later adopted by Berkeley scientists who claimed its discovery in 1959.

The International Union of Pure and Applied Chemistry (IUPAC) officially recognised the name nobelium following the Berkeley results.

In 1994, and subsequently in 1997, the IUPAC ratified the name nobelium (No) for the element on the basis that it had become entrenched in the literature over the course of 30 years and that Alfred Nobel should be commemorated in this fashion

A team working in Stockholm reported in 1957 an isotope whose atomic number is 102. They made this isotope by bombardment of ²⁴⁴Cm with ¹³C ions. They named the element nobelium after Alfred Nobel. In 1958 a group at Berkeley, California, USA reported that they were unable to reproduce this work, findings agreed by a Russian group at Dubna. However an authenticated discovery of nobelium was made in 1958 by Seaborg and others at Berkeley, California, USA. Since then a number of isotopes with mass numbers in the range 250-259 have been made.

The discovery of element 102 was first announced by physicists at the Nobel Institute in Sweden in 1957. The team reported that they created an isotope with a half-life of 10 minutes, decaying by emission of an 8.5 MeV alpha particle, after bombarding ²⁴⁴Cm with ¹³C nuclei. The activity was assigned to ²⁵¹No or ²⁵³No. The scientists proposed the name nobelium (No) for the new element. Later they retracted their claim and associated the activity to background effects.

The synthesis of element 102 was then claimed in April 1958 at the University of California, Berkeley, by Albert Ghiorso, Glenn T. Seaborg, John R. Walton and Torbjørn Sikkeland. The team used the new heavy-ion linear accelerator (HILAC) to bombard a curium target (95% ²⁴⁴Cm and 5% ²⁴⁶Cm) with ¹³C and ¹²C ions. They were unable to confirm the 8.5 MeV activity claimed by the Swedes but were instead able to detect decays from ²⁵⁰Fm, supposedly the daughter of ²⁵⁴102, which had an apparent half-life of ~3 s. In 1959 the team continued their studies and claimed that they were able to produce an isotope that decayed predominantly by emission of an 8.3 MeV alpha particle, with a half-life of 3 s with an associated 30% spontaneous fission branch. The activity was initially assigned to ²⁵⁴No but later changed to ²⁵²No. The Berkeley team decided to adopt the name nobelium for the element.

Physical properties

• Melting point: about 1100 [or 827 °C (1521 °F)] K – though this is speculation and has yet to be experimentally confirmed

Orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.7s²
• Shell structure:  2.8.18.32.32.8.2
• Term symbol:   ¹S₀
• Pauling electronegativity: 1.3 (Pauling units)
•  First ionization energy: 642 kJ mol^-1