- Bohrium (Bh) is a synthetic, radioactive element with atomic number 107, belonging to Group 7 of the periodic table, directly beneath rhenium and technetium.
- It is part of the transactinide series and belongs to the 6d transition metals. Its electron configuration is predicted as [Rn] 5f¹⁴ 6d⁵ 7s², consistent with its placement in Group 7, though relativistic effects may subtly affect its behavior. Bohrium is expected to exhibit a predominant oxidation state of +7, like rhenium, with lower states such as +4, +5, and +6 also possible.
- Its atomic structure consists of one hundred and seven protons, about one hundred and sixty-one to one hundred and sixty-four neutrons depending on the isotope, and one hundred and seven electrons arranged in seven shells. The most stable isotope, bohrium-270 (²⁷⁰Bh), has a half-life of about 61 seconds, while most others decay within fractions of a second to a few minutes.
- The discovery of bohrium was the result of international competition. In 1976, scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Soviet Union, reported possible evidence for element 107 by bombarding bismuth-209 (²⁰⁹Bi) with chromium-54 ions. However, the results were not conclusive. In 1981, a team led by Peter Armbruster and Gottfried Münzenberg at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany, successfully synthesized element 107 by bombarding bismuth-209 with nuclei of chromium-54. They produced bohrium-262 (²⁶²Bh), which decayed through alpha emission. This marked the confirmed discovery of bohrium.
- The naming of element 107 also generated debate. The German team proposed the name nielsbohrium (Ns) in honor of Danish physicist Niels Bohr, whose pioneering work on atomic structure and quantum theory transformed modern physics. The International Union of Pure and Applied Chemistry (IUPAC) later shortened the name to bohrium (Bh) for consistency and ease of use. In 1997, the name was officially adopted, ensuring Bohr’s legacy was honored in the periodic table.
- Bohrium has no practical applications due to its extreme instability and production in atom-scale quantities. Its importance lies in experimental nuclear chemistry and the study of trends in Group 7 elements, helping researchers test theoretical models of superheavy element chemistry.
- Chemically, bohrium is expected to resemble rhenium, forming volatile compounds such as bohrium(VII) oxide (Bh₂O₇) and halides like bohrium(VII) chloride (BhCl₇). Limited experiments with a few atoms suggest that its chemistry is indeed consistent with its placement, though relativistic effects may impart subtle differences compared to lighter homologues.
- Biologically, bohrium has no natural role and is considered highly radiotoxic. However, because it is created only in tiny amounts and decays rapidly, it poses no biological threat outside specialized laboratories.
- Environmentally, bohrium does not occur in nature. It is created artificially in particle accelerators, decays quickly, and has no environmental impact.
