Bohrium is a synthetic, highly radioactive transactinide element named after Niels Bohr. It does not occur in nature and is produced in particle accelerators; only minute amounts with very short half-lives have been observed.
Bohrium (Bh) is a synthetic transactinide with atomic number 107. It lies in Group 7 (the manganese–technetium–rhenium family) and in period 7. Because it does not exist in nature, it is created atom-by-atom in particle accelerators.
Bohrium is formed in fusion–evaporation reactions, where a heavy target is bombarded by a lighter ion. A stylized discovery route is:
\(^{209}\mathrm{Bi}(^{54}\mathrm{Cr},\,n)\,^{262}\mathrm{Bh}\)
The hot compound nucleus sheds n neutrons to reach a specific Bh isotope, which is then transported to detectors within milliseconds.
Freshly created Bh atoms recoil out of the target into a separator and are implanted into position-sensitive detectors. They are identified by time-correlated decay chains—mostly alpha decays and, at times, spontaneous fission—with characteristic energies.
\(^{A}_{107}\mathrm{Bh} \;\xrightarrow{\alpha}\; ^{A-4}_{105}\mathrm{Db} + \alpha \;\to\; \cdots\)
By analogy with its Group-7 congeners, +7 is expected to be the most stable high oxidation state for Bh, with access to +5 and +4 under reducing conditions. Atom-at-a-time studies indicate formation of volatile oxychlorides akin to rhenium, e.g., behavior consistent with ReO3Cl analogues (BhO3Cl) under chlorinating/oxidizing conditions.
Relativistic calculations and periodic trends suggest a ground-state configuration close to [Rn] 5f14 6d5 7s2, paralleling rhenium’s 5d5 6s2 arrangement but with significant relativistic effects in the 6d orbitals.
Direct aqueous chemistry is not established due to extreme scarcity and short half-lives. However, by Group-7 analogy, a +7 tetraoxo anion like \(\mathrm{BhO_4^-}\)
Several short-lived isotopes (e.g., mass numbers in the low-260s) have been reported. Dominant decay modes are alpha decay and spontaneous fission; half-lives typically range from milliseconds to seconds (sometimes minutes), depending on the isotope.
Experiments produce only a few atoms at a time, and they decay rapidly. This makes it impossible to prepare macroscopic samples to measure density, melting point, or crystal structure. Most insights come from single-atom chromatography and gas-phase thermochromatography.
Yes—Bohrium is a radiotoxic heavy element. Although experiments involve atom-scale quantities, work requires specialized separators, remote handling, shielding, and rigorous radiological controls to protect researchers and equipment.
Production (stylized fusion–evaporation):
\(^{209}\mathrm{Bi}(^{54}\mathrm{Cr},\,n)\,^{262}\mathrm{Bh}\)
Generic alpha decay:
\(^{262}\mathrm{Bh} \;\to\; ^{258}\mathrm{Db} + \alpha\)