107 seaborgiumbohriumhassium


Periodic Table - Extended Periodic Table
Name, Symbol, Number bohrium, Bh, 107
Chemical series transition metals
Group, Period, Block 7, 7, d
Appearance unknown, probably silvery
white or metallic gray
Atomic mass (272) g/mol
Electron configuration perhaps [Rn] 5f14 6d5 7s2
(guess based on rhenium)
Electrons per shell 2, 8, 18, 32, 32, 13, 2
Phase presumably a solid
CAS registry number 54037-14-8

Bohrium (IPA: /ˈbɔː(h)riəm/), also called eka-rhenium, is a chemical element in the periodic table that has the symbol Bh and atomic number 107. It is a synthetic element whose most stable isotope, Bh-272, has a half-life of 10 seconds.



It was synthesized in 1976 by a Soviet team led by Y. Oganessian at the Joint Institute for Nuclear Research at Dubna, who produced isotope 261Bh with a half-life of 1-2 ms (later data gave a half life of around 10 ms). They did this by bombarding bismuth-204 with heavy nuclei of chromium-54.

In 1981 a German research team led by Peter Armbruster and Gottfried Münzenberg at the Gesellschaft für Schwerionenforschung (Institute for Heavy Ion Research) in Darmstadt were also able to confirm the Soviet team's results and produce bohrium, this time the longer-lived Bh-262.

The Germans suggested the name nielsbohrium with symbol Ns to honor the Danish physicist Niels Bohr. The Soviets had suggested this name be given to element 105 (dubnium).

There was an element naming controversy as to what the elements from 101 to 109 were to be called; thus IUPAC adopted unnilseptium (IPA: /ˌjuːnɪlˈsɛptiəm/, symbol Uns) as a temporary, systematic element name for this element. In 1994 a committee of IUPAC recommended that element 107 be named bohrium. While this conforms to the names of other elements honoring individuals, where only the surname is taken, it was opposed by many who were concerned that it could be confused with boron. Despite this, the name bohrium for element 107 was recognized internationally in 1997.


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