Bohrium · element 107
Niels Bohr's element very nearly carried his first name too, until IUPAC trimmed it
Key facts
Bohrium honours Niels Bohr, the Danish physicist whose 1913 model of the atom first explained why electrons sit in shells and, with them, why the periodic table has the shape it does. It is fitting that an element made possible by his ideas about atomic structure sits near the edge of the table he helped explain.
Element 107 was first made in 1981 at GSI in Darmstadt, Germany, using a technique called cold fusion that had nothing to do with tabletop energy claims and everything to do with gently merging two nuclei. Five atoms were enough to prove it existed.
Where it is found
Bohrium occurs nowhere in nature. Its isotopes decay within seconds or, at best, a minute or so, so even if a bohrium atom had formed in some ancient cosmic event it would have vanished long before the Earth existed. Every atom studied has come out of an accelerator, and the grand total across all laboratories is probably in the hundreds rather than thousands.
The 1981 experiment fired chromium-54 ions at a bismuth-209 target, producing bohrium-262. The two nuclei were given just enough energy to fuse and no more, so the product did not fly apart. Later, chemists wanting longer-lived atoms bombarded berkelium-249 with neon-22 to make bohrium-267. Bohrium also appears as a link in the decay chains of nihonium and moscovium, made by firing calcium-48 at americium.
How it was discovered
A team at Dubna led by Yuri Oganessian claimed element 107 in 1976 after seeing spontaneous fission from a bismuth and chromium reaction, but fission alone cannot pin down which element was made. The convincing evidence came in 1981 from Peter Armbruster and Gottfried Munzenberg at GSI. Using a velocity filter called SHIP, they separated five atoms of bohrium-262 and traced their alpha decays down to known isotopes of dubnium and lawrencium. Credit went to GSI.
The German team suggested nielsbohrium, symbol Ns, using Bohr's full name to avoid confusion with boron. The Soviets had used the same name for element 105 during the naming disputes. In 1997 IUPAC approved the shorter bohrium, symbol Bh, noting that no other element uses a person's first name. Bohr himself had died in 1962, fifteen years before the element that bears his name was made.
What we use it for
Bohrium has no practical use and never will. Its purpose is to answer questions. The biggest is whether the periodic table's rules keep working when atoms become so heavy that their inner electrons move at a good fraction of the speed of light.
In 2000 a collaboration working at the Paul Scherrer Institute in Switzerland tested this directly. Using just six atoms of bohrium-267, they showed that bohrium reacts with oxygen and hydrogen chloride to form a volatile oxychloride, just as technetium and rhenium do, and that the bohrium compound is the least volatile of the three. That is exactly the trend group 7 predicts. Physicists also study its isotopes because their half-lives help map the route towards a predicted region of more stable superheavy nuclei.
Reading the numbers
Nothing about bulk bohrium has ever been measured, because there has never been a bulk sample. The atomic mass of 270 is the mass number of one of the longest-lived known isotopes, with a half-life of around a minute. The density of about 37 grams per cubic centimetre is a calculation. If correct it would be far denser than rhenium, the metal above it, and near the top of the entire table. The melting point, boiling point and electronegativity are simply unknown.
The predicted electron configuration [Rn] 5f14 6d5 7s2 gives seven electrons beyond the closed radon core, which is why bohrium sits in group 7 under manganese, technetium and rhenium. The expected highest oxidation state is +7, and the oxychloride experiment, where bohrium behaved as a +7 metal, is consistent with that. So far, bohrium is a well-behaved member of its group.
Safety and the environment
All bohrium is radioactive and short-lived. The longest-lived isotopes decay within a minute or two, so the element cannot build up anywhere. The few atoms produced each year are created inside shielded accelerator halls and detected through their own decay. Nobody outside those laboratories can ever come into contact with bohrium, and there is nothing to dispose of afterwards.
Did you know?
- Only five atoms of bohrium were detected in the 1981 discovery experiment, and that was enough to satisfy the international review.
- The chemistry of bohrium was first studied in 2000 using a total of six atoms, which formed a compound with oxygen and chlorine.
- Niels Bohr won the Nobel Prize in Physics in 1922. His son Aage Bohr won the same prize in 1975 for work on the structure of the nucleus.
- The symbol Ns for nielsbohrium appeared on some periodic tables for element 105 in the Soviet Union and for element 107 in Germany before IUPAC settled on Bh.
- Bohr's institute in Copenhagen sheltered many physicists fleeing Nazi Germany in the 1930s, and Bohr himself escaped to Sweden by boat in 1943.
More in the superheavy elements
The nearest neighbours of bohrium in the family, by atomic number.
See all 15 superheavy elements on one page, or browse all 118 elements. Also listed under the transition metals.
Frequently asked questions
Who is bohrium named after?
Niels Bohr, the Danish physicist who proposed the shell model of the atom in 1913 and won the Nobel Prize in Physics in 1922. The name was approved by IUPAC in 1997.
Why is it bohrium and not nielsbohrium?
The German discoverers proposed nielsbohrium to avoid any confusion with boron. IUPAC shortened it to bohrium in 1997 because no other element uses a person's first name, and the symbols Bh and B are already distinct.
How was bohrium discovered?
In 1981 a team at GSI in Darmstadt fired chromium-54 ions at a bismuth-209 target and detected five atoms of bohrium-262. They identified the element by following its chain of alpha decays down to known isotopes.
Is bohrium a metal?
It is expected to be a dense, solid metal like rhenium, and chemistry experiments show it forms compounds in the same way group 7 metals do. Nobody has ever had enough atoms to see it as a solid, so its appearance is unknown.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Bohrium reference article. Spotted an error? Tell us.