Bohrium (107)

Bohrium is a synthetic element that is not present in the environment at all.

The interested reader should consult the on-line version of The Wonderful World of Atoms and Nuclei for a fascinating insight into research on "super-heavy" atoms.

Name: Bohrium Symbol: Bh Atomic number: 107 Atomic weight: [ 272 ] Standard state: presumably a solid at 298 K CAS Registry ID: 54037-14-8

Group in periodic table: 7 Period in periodic table: 7 Block in periodic table: d-block Color: unknown, but probably metallic and silvery white or grey in appearance Classification: Metallic

Historical information

Bohrium was discovered by Peter Armbruster, Gottfried Münzenber and their co-workers in 1981 at the Gesellschaft für Schwerionenforschung (GSI), or the Institute for Heavy Ion Research in Darmstadt, Germany. The team bombarded a target of bismuth-209 with accelerated nuclei of chromium-54 to produce 5 atoms of the isotope bohrium-262. This substantiated the work done by USSR scientists in 1976, when an isotope of bohrium was produced.

The origin of name is Niels "Bohr", the Danish physicist. You may remember the Bohr’s model of electron shell structure. Originally, German scientists from the GSI suggested the name Nielsbohrium (symbol Ns) after Niels Bohr. IUPAC are happy to name an element after Bohr but suggested bohrium (Bh) on the grounds that the first name of a person does not appear in the names of any other element named after a person. This seems to have been accepted by all concerned.

However, this was opposed by the discoverers as there was some concern that the name might be confused with boron and in particular the distinguishing of the names of their respective oxyanions, bohrate and borate. The matter was handed to the Danish branch of IUPAC which, despite this, voted in favour of the name bohrium, and thus the name bohrium for element 107 was recognized internationally in 1997. The IUPAC subsequently decided that bohrium salts should be called bohriates instead of bohrates

Physical properties

• Density of solid: 27200 (predicted) kg m^-3
• Most physical properties of this element are as yet unknown

Orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.6d⁵.7s² (a guess based upon that of rhenium)
• Shell structure:  2.8.18.32.32.13.2
• Term symbol:   ⁶S_5/2 (a guess based upon guessed electronic structure)

Isolation

Only a few atoms of element 107, bohrium, have ever been made. The first atoms were made through a nuclear reaction involving fusion of an isotope of lead, ²⁰⁹Pb, with one of chromium, ⁵⁴Cr.

²⁰⁹Pb + ⁵⁴Cr → ²⁶²Bh + ¹n

Isolation of an observable quantity of bohrium has never been achieved, and may well never be. This is because bohrium decays very rapidly through the emission of α-particles.

More recently, other isotopes have been made at the Paul Scherrer Institute (PSI) in Switzerland.

²⁴⁹Bk + ²²Ne → ²⁶⁶Bh + 5¹n

²⁴⁹Bk + ²²Ne → ²⁶⁷Bh + 4¹n

In this work, it appears the scientists concerned feel bohrium forms the oxychloride BhClO₃.