Bohrium, the element named for Niels Bohr, has atomic number 107.
Atomic number counts the protons in an atom’s nucleus, so every bohrium atom contains 107 protons. Bohrium is represented by the symbol Bh and belongs to group 7 of the periodic table, alongside manganese, technetium and rhenium.
It is a synthetic, highly radioactive transactinide element and does not occur naturally in useful quantities. Scientists create it in particle accelerators, where heavy nuclei are fused and the resulting atoms are identified through radioactive decay chains. Only very small numbers of atoms have been produced.
The naming process caused a minor controversy. The discoverers initially proposed “nielsbohrium,” but IUPAC adopted “bohrium” in 1997, following a preference for not using a scientist’s complete name. The name honours Bohr’s foundational work on atomic structure and quantum theory, not the element’s everyday chemical abundance.