242 22 260 Pu+ Ne---> 104+4n 94 10

Element l04, the first transactinide element, is expected to have chemical properties similar to those of hafnium. It would, for example, form a relatively volatile compound with chlorine (a tetrachloride). The Soviet scientists have performed experiments aimed at chemical identification, and have attempted to show that the 0.3-s activity is more volatile than that of the relatively nonvolatile actinide trichlorides. This experiment does not fulfill the test of chemically separating the new element from all others, but it provides important evidence for evaluation. New data, reportedly issued by Soviet scientists; have reduced the half-life of the isotope they worked with from 0.3 to 0.15 s. The Dubna scientists suggest the name kurchatovium and symbol Ku for Element lO4, in honor of Igor Vasilevich Kurchatov (1903-1960), late head of Soviet Nuclear Research. The Dubna Group also has proposed the name dubnium for Element 104. In 1969, Ghiorso, Nurmia, Harris, K. A. Y. Eskola, and P. L. Eskola of the University of California at Berkeley reported they had positively identified two, and possibly three, isotopes of Element 104. The group also indicated that after repeated attempts so far they have been unable to produce isotope 260-104 reported by the Dubna groups in 1964. The discoveries at Berkeley were made by bombarding a target of 249Cf With 12C nuclei of 71 MeV, and 13C nuclei of 69 MeV. The combination of 12C with 249Cf followed by instant emission of four neutrons produced Element 257-104. This isotope has a half-life of 4 to 5 s, decaying by emitting an alpha particle into 253No, with a half-life of 105 s. The same reaction, except with the emission of three neutrons, was thought to have produced 258-104 with a half-life of about 1/100 s. Element 259-104 is formed by the merging of a 13C nuclei with 249Cf, followed by emission of three neutrons. This isotope has a half-life of 3 to 4 s, and decays by emitting an alpha particle into 255No, which has a half-life of 185 s. Thousands of atoms of 257-104 and 259-104 have been detected. The Berkeley group believe their identification of 258-104 was correct. As of January 1995 it was thought that eleven isotopes of Element 104 have been identified. The Berkeley group proposed for the new element the name rutherfordium (symbol Rf), in honor of Ernest Rutherford, New Zealand physicist. The claims for discovery and the naming of Element 104 are still in question. The International Union of Pure and Applied Physics proposed using the neutral temporary name, unnilquadium" and more recently has reconunended the name dubnium, with symbol Db, be used, even though many scientists have used the name rutherfordium for many years. The naming of this element is not yet settled.