Bohrium

Physical properties

Unnilseptium, or bohrium, is artificially produced one atom at a time in particle accelerators.In 1976 Russian scientists at the nuclear research laboratories at Dubna synthesizedelement 107, which was named unnilseptium by IUPAC. Only a few atoms of element 107were produced by what is called the “cold fusion” process wherein atoms of one element areslammed into atoms of a different element and their masses combine to form atoms of a newheavier element. Researchers did this by bombarding bismuth-204 with heavy ions of chromium-54 in a cyclotron. The reaction follows: Bi-209 + Cr-54 + neutrons = (fuse to form)Uns-262 + an alpha decay chain.
The melting point, boiling point, and density of element 107, as well as some other properties,are not known because of the small number of atoms produced.

Isotopes

There are a total of 10 isotopes of unnilseptium (bohrium). Not all their half-livesare known. However, the ones that are known range from 8.0 milliseconds to 9.8 secondsfor Bh-272, which is the most stable isotope of bohrium and which decays into dubnium-268 through alpha decay. Only one isotope, Uns-261, has a decay mode that involvesboth alpha decay and spontaneous fission. All the others decay by alpha emission.

Origin of Name

Named after the scientist Niels Bohr.

History

Bohrium is expected to have chemical properties similar to rhenium. This element was synthesized and unambiguously identified in 1981 using the Universal Linear Accelerator (UNILAC) at the Gesellschaft für Schwerionenforschung (G.S.I.) in Darmstadt, Germany. The discovery team was led by Armbruster and Münzenberg. The reaction producing the element was proposed and applied earlier by a Dubna Group led by Oganessian in 1976. A target of 209Bi was bombarded by a beam of 54Cr ions. In 1983 experiments at Dubna using the 157-inch cyclotron, produced 262107 by the reaction 209Bi + 54Cr. The alpha decay of 246Cf, the sixth member in the decay chain of 262107, served to establish a 1-neutron reaction channel. The IUPAC adopted the name Bohrium with the symbol Bh for Element 107 in August 1997. Five isotopes of bohrium are now recognized. One isotope of bohrium appears to have a relatively long life of 15 seconds. Work on this relatively longlived isotope has been performed with the 88-inch cyclotron at the Lawrence-Berkeley National Laboratory.

The Uses of Bohrium

None, except for research purposes.

Definition

A synthetic radioactive element first detected by bombarding a bismuth target with chromium nuclei. Only a small number of atoms have ever been produced.

Definition

bohrium: Symbol Bh. A radioactivetransactinide element; a.n. 107. Itwas first made in 1981 by Peter Armbrusterand a team in Darmstadt,Germany, by bombarding bismuth-209 nuclei with chromium-54 nuclei.Only a few atoms of bohrium haveever been detected.

Hazard

Even though most isotopes of unnilseptium are alpha emitters, there is little radiationhazard because only a few atoms have been produced.