107 Bh Bohrium 272*
Transition metal d-block Period 7 Group 7 Radioactive Synthetic

Bohrium

Bh · Element 107 · Manganese group

A superheavy element whose chemistry, tested one atom at a time, behaves as predicted for group 7.

STATE AT 20°C Solid
ATOMIC MASS 272 u
ELECTRON CONFIGURATION [Rn] 5f¹⁴ 6d⁵ 7s²

Structure

The bohrium atom

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.

Orbital cloud

Measured values

Property sheet

Every bar shows where bohrium sits among all 118 elements for that property.

Physical

Density 37.1 g/cm³~ 98%
Melting point
Boiling point
Specific heat
Thermal conductivity

Atomic

Atomic radius 247 pm~ 85%
Covalent radius 141 pm
Van der Waals radius 247 pm~

Electronic

Electronegativity
Ionisation energy 742.9 kJ/mol 59%
Electron affinity

Occurrence

Abundance in crust 0 mg/kg 0%

Identity

SymbolBh
Atomic number107
Atomic mass272 u
CategoryTransition metal
Blockd
Crystal structureunknown
Oxidation states+7
Discovered1981
Discovered byGSI Darmstadt

Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.

Size, to scale

How big is a bohrium atom?

Radius 247 pm — that is 0.247 nm, so about 2024 million of them side by side would span a millimetre.

Thermal range

Solid, liquid, gas — and when

Neither transition has been measured for bohrium — too few atoms have ever existed at once.

Where it sits

Position in the table

Bohrium sits in period 7, group 7. Everything in group 7 shares the same outer-electron count, which is why they behave so similarly.

OTHER TRANSITION METALS

All transition metals

The story

What bohrium is, and how we found it

A superheavy element whose chemistry, tested one atom at a time, behaves as predicted for group 7.

The discovery of bohrium

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 "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, and proposed the name "nielsbohrium." 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

What bohrium is used for

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 extreme 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 extremes 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

Natural occurrence

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 extraordinary 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. The most stable known isotope, bohrium-270, has a half-life of approximately 61 seconds, meaning that half of any sample will decay within about one minute of creation. Other isotopes of bohrium have even shorter half-lives, with some lasting only milliseconds before undergoing radioactive decay. The element's extreme rarity means that all bohrium research must be conducted on individual atoms or very small numbers of atoms, requiring incredibly 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

Safety

Bohrium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.

Bohrium presents unique safety challenges due to its extreme radioactivity, though the primary hazard comes not from the element itself but from the high-energy radiation and nuclear processes involved in its production and study. The element's intense radioactivity requires specialized radiation safety protocols and containment systems designed for handling highly radioactive materials in research environments. Personnel working with bohrium must wear appropriate radiation monitoring equipment and follow strict protocols for minimizing exposure to ionizing radiation. The short half-life of bohrium means that samples quickly decay into other radioactive elements, creating a complex mixture of decay products that require careful monitoring and containment. Facilities producing bohrium must be equipped with sophisticated radiation shielding, ventilation systems, and waste management capabilities designed for highly radioactive materials. The primary safety concern is not direct contact with bohrium atoms, which exist in such small quantities as to be negligible, but rather exposure to the intense radiation fields associated with its production and decay. Workers in bohrium research facilities must undergo specialized training in radiation safety and emergency response procedures for radioactive material incidents. The research environment requires continuous monitoring of radiation levels and strict adherence to ALARA (As Low As Reasonably Achievable) principles for radiation exposure. Emergency procedures must be in place for potential accidents involving radioactive contamination or equipment failures in accelerator facilities. Waste products from bohrium research require long-term storage and monitoring due to the presence of various radioactive decay products with different half-lives. The extremely small quantities of bohrium produced mean that conventional chemical toxicity is not a significant concern, but radiation safety remains paramount. Pregnant women and individuals under 18 are typically excluded from areas where bohrium research is conducted due to increased radiation sensitivity.

Quick answers

Bohrium: common questions

What is Bohrium?

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.

What is the electron configuration of Bohrium?

Bohrium's ground-state electron configuration is [Rn] 5f¹⁴ 6d⁵ 7s², giving 7 occupied shells holding 2, 8, 18, 32, 32, 13, 2 electrons respectively.

What is the atomic mass of Bohrium?

Bohrium has no stable isotope, so it has no standard atomic weight. The figure quoted, 272, is the mass number of its longest-lived known isotope.

How dense is Bohrium?

Bohrium has a density of 37.1 g/cm³. Water is 1.0 g/cm³, so a block of bohrium is about 37.1× heavier.

Who discovered Bohrium, and when?

Bohrium was discovered in 1981 by GSI Darmstadt. It is named after niels Bohr.

How common is Bohrium on Earth?

Bohrium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.

Is Bohrium radioactive?

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.