|Atomic mass||(262) amu|
Dubnium is element 105. In 1967, the Soviets at the Joint Institute for Nuclear Research claimed to have produced a few atoms of element-105 by bombarding 243Am with ions of 22Ne. By 1970, an American group at the Lawrence Berkeley Laboratory reported positive identification of the element and suggest the name "hahnium", after a German chemist, Otto Hahn. Their method was by bombardment of 249Cf with ions of 15N. By 1971, the same group announced the positive synthesis of the five other isotopes of hahnium.
Recently, in March of 1997, the International Union of Pure and Applied Chemistry (IUPAC) recommended that element-105, which has been unofficially known as "hahnium" for about 25 years, be named "dubnium" in honour of the Joint Institute for Nuclear Research in Dubna, Russia, where important contributions to the creation of transfermium elements. However, scientists may continue to use hahnium for element-105 even if the name change has gone through.
In recommending that element-105 be named "dubnium", IUPAC has cast the name "hahnium" into oblivion. This is avoid greater confusion because an element name that has been widely used in the literature should not be reassigned to a different element.