| 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. |
| Uses | 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. |