|Boiling Point: unknown
Melting Point: unknown
Electrons Energy Level: 2, 8, 18, 32, 32, 11, 2
Isotopes: 16 + None Stable
Heat of Vaporization: unknown
Heat of Fusion: unknown
Specific Heat: unknown
Atomic Radius: unknown
Ionic Radius: unknown
Vapor Pressure: unknown
|1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d10f14 6s2p6d3 7s2|
Dubnium (named after Dubna, Russia) was reportedly first synthesized by G. N. Flerov in 1967 at the Joint Institute for Nuclear Research in Dubna, Russia (reportedly producing nuclide 260105 and nuclide 261105 by bombarding 243Am with 22Ne). Their evidence was based on time-coincidence measurements of alpha energies. It was reported that early in 1970 Dubna scientists synthesized Element 105 and that by the end of April 1970 "had investigated all the types of decay of the new element and had determined its chemical properties". The Soviet group proposed the name joliotium for Element 105.
In late April 1970, it was announced that Albert Ghiorso, Nurmia, Haris, K.A.Y. Eskola, and P.L. Eskola, working at the University of California at Berkeley, had positively identified element 105. The discovery was made by bombarding a target of 249Cf with a beam of 84 MeV nitrogen nuclei in the Heavy Ion Linear Accelerator (HILAC) a particle accelerator. When a 15N nuclear is absorbed by a 249Cf nucleus, four neutrons are emitted and a new atom of 260105 with a half-life of 1.6 s is formed. While the first atoms of Element 105 are said to have been detected conclusively on March 5, 1970, there is evidence that Element 105 had been formed in Berkeley experiments a year earlier by the method described.
The Berkeley scientists later tried to confirm the Soviet findings using more sophisticated methods but were not successful. They proposed that the new element should be named hahnium (symbol Ha) in honor of the late German scientist Otto Hahn (1879 - 1968). Consequently this was the name that most American and Western European scientists used.
In October 1971, it was announced that two new isotopes of Element 105 were synthesized with the heavy ion linear accelerator by A. Ghiorso and co-workers at Berkeley. Element 261105 was produced both by bombarding 250Cf with 15N and by bombarding 249Bk with 16O. The isotope emits 8.93-MeV alpha particles and decays to 257Lr with a half-life of about 1.8 seconds. Element 262105 was produced by bombarding 249Bk with 18O. It emits 8.45 MeV alpha particles and decays to 258Lr with a half-life of about 40 seconds. Fifteen isotopes of Element 105 are now recognized. In 1994 the International Union of Pure and Applied Chemistry recommended the name joliotium for Element 105; however, the matter was not settled.
An element naming controversy erupted over what to name this element after Russian researchers protested. The International Union of Pure and Applied Chemistry (IUPAC) thus adopted unnilpentium, symbol Unp, as a temporary, systematic element name. However, in 1997 they resolved the dispute and adopted the current name, dubnium (symbol Db), after the city that contains the Russian Joint Institute for Nuclear Research. Its former names have included hahnium, joliotium and nielsbohrium.
Dubnium , also called eka-tantalum is a highly radioactive synthetic element whose most stable isotope has a half-life of 32 hours, 268Db. This relatively high stability compared to the surrounding elements on the periodic table gives evidence that by manipulating the number of neutrons in a nucleus, one can alter the stabilities of such nuclei.