Element Rutherfordium (kurchatovium, unnilquadium), Rf

According to Seaborg's theory similarity in electronic structures of transuranium elements and those of lanthanoides (both of them are f-block elements, corresponding to the filling of the 4f electron shell in lanthanoides and 5f in transuranium elements of actinoids series) the element 104 should be analogous of elements of titanium, zirconium and hafnium subgroups (d-block elements, with correspondingly 4, 5 and 6d layers filling) and could be synthesized following the reaction:

²⁴²₉₄Pu + ²²₁₀Ne -> ²⁶⁰₁₀₄Rf + 4⁰n

The problem of this synthesis was the subject of research of the group of Soviet physicist under leadership of Georgy Nikolaevich Flerov in Joint Institute for Nuclear Research (JINR) at Dubna, Russia. The element 104 was synthesized in 1964 by bombardment of plutonium with neon ions on the special multiply charged ion accelerator.

There history of the name is controversial. Since the Soviet scientists claimed that it was first detected in Dubna, dubnium was suggested, as was kurchatovium after Igor Vasilevitch Kurchatov, head of the Soviet Nuclear Research, meanwhile systematic International Union of Pure and Applied Chemistry (IUPAC) name unnilquadium for the element 104. In 1994 IUPAC proposed the name dubnium because it was first discovered Dubna. The American Chemical Society proposed Rutherfordium, the name given by Ghiorso et al. in 1969. The latter became also the current IUPAC name. Dubnium was then used for element #105. The name and symbol Rutherfordium was then confirmed by the IUPAC for the element 104 in1997.