Dubnium

Dubnium’s (Unp) most stable isotope, Db-268, is unstable with a half-life of 16 hours. Itcan change into lawrencium-254 by alpha decay or into rutherfordium-268 by electron capture.Both of these reactions occur through a series of decay processes and spontaneous fission(SF). Since so few atoms of unnilpentium (dubnium) are produced, and they have such a shorthalf-life, its melting point, boiling point, and density cannot be determined. In addition, itsvalence and oxidation state are also unknown.

There are a total of 15 isotopes of unnilpentium (dubnium). Their half-livesrange from 0.76 seconds (for Db-257) to 16 hours (for Db-268). All of them decay byspontaneous fission and alpha decay.

Unnilquadium follows the transitional naming system of IUPAC but originally was named “hahnium” by the Berkeley group in honor of Otto Hahn, who discovered nuclear fission. The American Chemical Society endorsed the name “hahnium” for element 105, but as the Berkeley group continued its work and more isotopes of ₁₀₅Unp were formed, the IUPAC changed the name “hahnium” to “dubnium” after the city Dubna, Russia, where the first isotopes of unnilpentium were formed.

N. Flerov reported that a Soviet team working at the Joint Institute for Nuclear Research at Dubna may have produced a few atoms of ²⁶⁰105 and ²⁶¹105 by bombarding ²⁴³Am with ²²Ne. Their evidence was based on time-coincidence measurements of alpha energies. More recently, it was reported that early in 1970 Dubna scientists synthesized Dubnium 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.” In late April 1970, it was announced that Ghiorso, Nurmia, Harris, K. A. Y. Eskola, and P. L. Eskola, working at the University of California at Berkeley, had positively identified Dubnium. 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). When a 15N nucleus 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. Ghiorso and his associates have attempted to confirm Soviet findings by more sophisticated methods without success. 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 α particles and decays to ²⁵⁷Lr with a half-life of about 1.8 s. Element ²⁶²105 was produced by bombarding ²⁴⁹Bk with 18O. It emits 8.45 MeV α particles and decays to ²⁵⁸Lr with a half-life of about 40 s. Nine isotopes of Dubnium are now recognized. Soon after the discovery the names Hahnium and Joliotium, named after Otto Hahn and Jean-Frederic Joliot and Mme. Joliot-Curie, were suggested as names for Element 105. The IUPAC in August 1997 finally resolved the issue, naming Element 105 Dubnium with the symbol Db. Dubnium is thought to have properties similar to tantalum.

There are no uses for unnilpentium (dubnium) except for research purposes.

A radioactive synthetic element made by bombarding ²⁴⁹Cf nuclei with ¹⁵N atoms. It was first reported by workers at Dubna, a town near Moscow. Symbol: Db; p.n. 105; most stable isotope ²⁶²Db (half-life 34 s).

dubnium: Symbol Db. A radioactivetransactinide element; a.n. 105. Itwas first reported in 1967 by a groupat Dubna near Moscow and wasconfirmed in 1970 at Dubna and atBerkeley, California. It can be madeby bombarding californium–249 nucleiwith nitrogen–15 nuclei. Only afew atoms have ever been made.

The hazards of dubnium are similar to all radioactive heavy metals of the transactinideseries, but there is no threat to the public given that such a small amount of the element isproduced and exists.