ノーベリウム

解説ノーベリウム,No．原子番号102の元素．電子配置[Rn]5f 147s2の周期表3族アクチノイド元素．現在，知られている同位体核種は，250～264の範囲に15種．質量数259のα崩壊核種がもっとも長寿命で半減期58 min．第一イオン化エネルギー660 kJ mol－1(6.84 eV)．酸化数2，3．

来歴The name of No derives from “Alfred Nobel”, the discoverer of dynamite and founder of the Nobel prizes. It was first synthesized in 1966 by the Russian scientists from the JINR (Joint Institute for Nuclear Research) lab in Dubna, Russia under Georgi Flerov. Earlier claims to have synthesized “Nobelium” beginning in 1957 were shown to be erroneous but the original name was retained because of its widespread use throughout the scientific literature. 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 A. Ghiorso, T. Sikkeland, G. T. Seaborg and J. R. Walton at Berkeley, California. Since then a number of isotopes with mass numbers in the range 250–259 have been made. The longest half-life associated with this unstable element is 58 minute 259No.