Bh · Element 107 · Transition metal
A superheavy element whose chemistry, tested one atom at a time, behaves as predicted for group 7.
Structure
Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.
Measured values
Every bar shows where bohrium sits among all 118 elements for that property.
Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.
Same element, different neutrons
All bohrium atoms have the same number of protons, 107, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Bh-278, has 171 neutrons and a half-life of ~19 min.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Bh-267 | 160 | — | 14 sec | α, SF |
| Bh-270 | 163 | — | ~1.0 min | α |
| Bh-272 | 165 | — | 10.5 sec | α |
| Bh-274 | 167 | — | 44 sec | α |
| Bh-278 longest-lived | 171 | — | ~19 min | SF, α |
Periodic tables list 272 for bohrium: the mass number of one long-lived isotope, not an average, so mass minus atomic number gives 165, the neutron count of Bh-272.
Decay modes
~ marks a half-life whose published uncertainty is larger than the value itself.
Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.
Size, to scale
Radius 247 pm — that is 0.247 nm, so about 2.02 million of them side by side would span a millimetre.
Thermal range
Neither transition has been measured for bohrium — too few atoms have ever existed at once.
The story
A superheavy element whose chemistry, tested one atom at a time, behaves as predicted for group 7.
Bohrium was first synthesized in 1981 by a team of German scientists led by Peter Armbruster and Gottfried Münzenberg at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, using advanced heavy-ion accelerator technology. The discovery involved bombarding bismuth-209 targets with chromium-54 ions accelerated to extremely high energies, creating bohrium-262 through nuclear fusion reactions. The German team used sophisticated detection equipment to identify the characteristic decay signatures of bohrium atoms, confirming the creation of element 107 through careful analysis of radioactive decay chains. The element was initially given the temporary name "unnilseptium" (meaning "one-zero-seven" in Latin) according to International Union of Pure and Applied Chemistry (IUPAC) systematic naming conventions for undiscovered elements. The German research team proposed the name "nielsbohrium", which IUPAC shortened to "bohrium", in honor of Danish physicist Niels Bohr, who made fundamental contributions to atomic theory and quantum mechanics. However, the naming of element 107 became controversial when a Soviet team at the Joint Institute for Nuclear Research in Dubna claimed to have synthesized the element earlier, in 1976. The dispute over priority and naming lasted for years, with both teams presenting evidence for their claims and the scientific community carefully evaluating the experimental data. IUPAC ultimately recognized the German team's claim based on the quality and reproducibility of their experimental evidence, officially adopting the name "bohrium" with the symbol "Bh" in 1997. The discovery of bohrium represented a significant achievement in superheavy element research, demonstrating the ability to create and identify elements at the very limits of nuclear stability. The collaborative effort involved multiple institutions and represented years of technological development in accelerator physics and nuclear detection methods. This discovery paved the way for the synthesis of even heavier elements and advanced our understanding of the fundamental limits of atomic structure.
Applications
Bohrium, being an extremely short-lived synthetic superheavy element with a half-life measured in seconds, has no practical applications outside of fundamental scientific research. The element exists solely for advancing our understanding of nuclear physics, atomic structure, and the theoretical limits of matter. Research facilities use bohrium to study the properties of superheavy elements and test theoretical predictions about nuclear stability and the proposed "island of stability" where certain superheavy nuclei might have longer half-lives. The element serves as a crucial test case for nuclear models that predict the behavior of matter under harsh conditions, helping scientists understand how protons and neutrons interact in very heavy nuclei. Bohrium research contributes to our knowledge of nuclear shell structure and the magic numbers that determine nuclear stability, providing insights that could lead to the discovery of longer-lived superheavy elements. The study of bohrium's chemical properties, though extremely challenging due to its short half-life, helps validate theoretical predictions about how superheavy elements should behave chemically and their placement in the periodic table. This research has implications for understanding the fundamental limits of atomic structure and whether stable superheavy elements might exist with properties useful for future technologies. The techniques developed for detecting and studying bohrium have advanced nuclear physics instrumentation and methodology, contributing to improvements in particle detection and nuclear analysis capabilities. While bohrium itself has no current practical applications, the knowledge gained from its study contributes to nuclear physics research that underlies many important technologies, including nuclear power, medical isotopes, and materials science. Future applications might emerge if longer-lived isotopes of bohrium or related superheavy elements are discovered, potentially offering unique properties for specialized technological applications. The element's study also contributes to our understanding of stellar nucleosynthesis and the processes that create heavy elements in the universe.
Bohrium has no practical applications in everyday life or industry due to its extremely short half-life and the minute quantities that can be produced in particle accelerators. The element is used exclusively in advanced nuclear physics research at major scientific institutions equipped with heavy-ion accelerators. Research laboratories study bohrium to understand the fundamental properties of superheavy elements and test theoretical models of nuclear structure. The element serves as a benchmark for validating computational models that predict the behavior of matter at the limits of atomic mass. Nuclear physicists use bohrium research to explore the theoretical "island of stability" where superheavy elements might have longer half-lives and potentially useful properties. The study of bohrium contributes to advancing particle accelerator technology and detection methods for studying rare nuclear events. Educational institutions use bohrium as a teaching example of modern nuclear physics and the ongoing quest to understand the limits of atomic structure. Scientific publications and databases rely on bohrium research to update and refine theoretical models of nuclear physics and chemistry. International collaborations study bohrium to advance global understanding of superheavy element synthesis and properties. The element's discovery and study demonstrate the capabilities of modern nuclear physics facilities and international scientific cooperation. While bohrium itself cannot be used practically, research into its properties advances the fundamental science that underlies many nuclear technologies. The methodologies developed for bohrium research contribute to improvements in nuclear medicine, nuclear power, and materials science through better understanding of nuclear processes.
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
Bohrium does not occur naturally on Earth and must be artificially created in particle accelerators through nuclear fusion reactions, making it one of the rarest substances that can be produced by human technology. The element is synthesized by bombarding heavy target nuclei with lighter projectile nuclei at extremely high energies, typically using bismuth-209 targets and chromium-54 projectiles to create bohrium-262 through nuclear fusion. The production of bohrium requires sophisticated particle accelerator facilities capable of accelerating ions to precise energies and directing them onto target materials with high precision. Only a few atoms of bohrium can be produced at a time, even with the advanced accelerator technology, making it impossible to accumulate measurable quantities of the element. Bohrium-270, one of the longest-lived known isotopes, has a half-life of approximately 61 seconds, meaning that half of any sample will decay within about one minute of creation. Most other isotopes of bohrium have shorter half-lives, with some lasting only milliseconds before undergoing radioactive decay. The element's rarity means that all bohrium research must be conducted on individual atoms or very small numbers of atoms, requiring very sensitive detection equipment. Production facilities for bohrium exist at only a handful of locations worldwide, including the GSI Helmholtz Centre for Heavy Ion Research in Germany and the RIKEN laboratory in Japan. The synthetic nature of bohrium means that it has no geological distribution or natural reservoirs, existing only in the controlled environment of nuclear physics laboratories. Environmental concentrations of bohrium are essentially zero, as the element cannot persist in nature due to its rapid radioactive decay. The total amount of bohrium ever produced by humanity would be far too small to see with the naked eye, representing perhaps a few thousand atoms created over decades of research. Future production might increase as accelerator technology advances, but bohrium will likely remain one of the rarest substances known to science.
Handling
Bohrium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Bohrium is radioactive, but it is made only a few atoms at a time in heavy-ion accelerators. Its isotopes decay by alpha emission and spontaneous fission; bohrium-270, for example, has a half-life of about one minute. No weighable amount of bohrium has ever existed, so the atoms themselves cannot deliver a meaningful radiation dose to anyone, and chemical toxicity does not arise at these quantities. The hazards in this research come from the experiment, not the element: the accelerator beam, radioactive targets and activated equipment, and the waste these produce, which is managed as radioactive waste under national radiation protection rules. Staff follow the standard occupational radiation rules: annual dose limits, personal dose monitoring and keeping doses as low as reasonably achievable (ALARA). Workers under 18 face much lower dose limits than adults: one tenth of the adult limits under US Nuclear Regulatory Commission rules (10 CFR 20.1207), and 1 mSv a year at US Department of Energy laboratories (10 CFR 835.207). A worker who declares a pregnancy is limited to 5 mSv to the fetus over the whole pregnancy (10 CFR 20.1208 and 835.206).
Quick answers
Bohrium (symbol Bh) is element 107 on the periodic table, a transition metal in period 7, group 7. A superheavy element whose chemistry, tested one atom at a time, behaves as predicted for group 7. At room temperature it is a solid, and it is radioactive.
[Rn] 5f¹⁴ 6d⁵ 7s², giving 7 occupied shells with the distribution 2, 8, 18, 32, 32, 13, 2.Bohrium has no stable isotope, so it has no standard atomic weight. The figure quoted, 272, is the mass number of Bh-272, the isotope periodic tables usually list; the longest-lived one in the IAEA data is Bh-278.
Bohrium has no stable isotope. Its longest-lived known isotope, Bh-278, has 171 neutrons (mass number 278 minus atomic number 107) and a half-life of ~19 min. Periodic tables list 272 for bohrium, the mass number of one long-lived isotope, so mass minus atomic number gives 165, the neutron count of Bh-272.
Bohrium is predicted to have a density of about 37.1 g/cm³, though no sample large enough to weigh has ever been made. Water is 1.0 g/cm³ for comparison.
Bohrium was discovered in 1981 by GSI Darmstadt. Origin of the name: Niels Bohr.
Bohrium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.
Yes. Bohrium has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.