Db · Element 105 · Transition metal
Named after Dubna, the Russian town where much of superheavy chemistry was pioneered.
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 dubnium 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 dubnium atoms have the same number of protons, 105, and differ only in their number of neutrons: those variants are its isotopes. None of them is stable. The longest-lived known isotope, Db-268, has 163 neutrons and a half-life of 28 hr.
| ISOTOPE | Neutrons | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|---|
| Db-262 | 157 | — | 35 sec | α |
| Db-266 | 161 | — | ~0.4 hr | SF |
| Db-267 | 162 | — | ~79 min | SF, α |
| Db-268 longest-lived | 163 | — | 28 hr | SF |
| Db-270 | 165 | — | 15 hr | SF |
Here the classroom shortcut, rounded atomic mass (268) minus atomic number, gives the same answer: 163.
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 dubnium — too few atoms have ever existed at once.
The story
Named after Dubna, the Russian town where much of superheavy chemistry was pioneered.
Dubnium's discovery became another intense Cold War rivalry between Soviet scientists at Dubna and American researchers at Berkeley. Both teams claimed priority in creating element 105, leading to competing names and a decades-long controversy resolved by international committee.
In 1968, Georgy Flerov's team at the Joint Institute for Nuclear Research reported creating element 105 by bombarding americium-243 with neon-22 ions. They proposed naming it "nielsbohrium" after Danish physicist Niels Bohr, pioneer of atomic structure theory.
In 1970, Albert Ghiorso's team at Berkeley Lab reported independent synthesis using californium-249 bombarded with nitrogen-15 ions. They proposed "hahnium" honoring German chemist Otto Hahn, discoverer of nuclear fission, creating a diplomatic naming dilemma.
IUPAC resolved the controversy by adopting "dubnium" in 1997, honoring the Russian research city Dubna where the Joint Institute for Nuclear Research is located. This decision recognized both teams' contributions while selecting a geographically neutral name.
Recent advanced detection techniques have confirmed dubnium's properties and enabled discovery of new isotopes, including the 2025 identification of dubnium-255 with detailed fission studies, validating theoretical predictions about superheavy nuclear behavior.
Applications
Dubnium serves as a crucial test subject for understanding chemical periodicity in superheavy elements, helping scientists determine how chemical properties change under very high nuclear charge conditions. Research focuses on validating theoretical predictions about Group 5 chemistry in the superheavy region.
Scientists use dubnium to investigate spontaneous fission processes and nuclear stability limits. The recent discovery of dubnium-255 provides new insights into odd-Z isotope fission behavior, contributing to understanding of nuclear structure at the limits of atomic existence.
Dubnium enables new studies of relativistic chemistry where electron speeds approach significant fractions of light velocity due to very high nuclear charge. These studies validate quantum mechanical calculations and predict chemical behavior of even heavier undiscovered elements.
Research teams employ dubnium data to test and refine theoretical nuclear models that predict superheavy element properties, stability, and optimal synthesis pathways. This research guides future attempts to create elements in the predicted "island of stability."
Dubnium studies drive innovation in superheavy element production methods, including optimization of ion beam energies, target preparation techniques, and separation chemistry for isolating individual atoms from complex reaction products.
Dubnium applications remain confined to specialized nuclear research laboratories including GSI Helmholtz Centre, Berkeley Lab, RIKEN, and the Flerov Laboratory at JINR Dubna. These institutions use dubnium for fundamental superheavy element physics and chemistry research.
Research teams utilize dubnium in precision nuclear measurements including alpha-decay spectroscopy, gamma-ray detection, and nuclear lifetime determination. These experiments provide essential data for understanding nuclear structure in the superheavy element region.
Scientists perform pioneering atom-at-a-time chemistry with dubnium, investigating chemical properties using advanced chromatography and extraction techniques. These studies represent the frontier where individual atoms can be chemically characterized.
Dubnium research necessitates development of ultra-sensitive detection systems including magnetic separators, time-of-flight analyzers, and sophisticated particle identification systems that push the boundaries of nuclear instrumentation capabilities.
Where it comes from
0 mg/kg of Earth's crust · more abundant than 0% of elements
Dubnium is known only from artificial nuclear synthesis in advanced particle accelerators. This superheavy element has never been found in nature.
Scientists create dubnium by bombarding californium-249 targets with nitrogen-15 ions, or by bombarding americium-243 with neon-22 ions in linear accelerators. These fusion reactions require precise energy calibration to overcome enormous electrostatic barriers.
The most stable dubnium isotope, 268Db, has a half-life of only 1.2 days, while most isotopes decay within seconds or minutes. The recently discovered 255Db demonstrates the range of nuclear stability in odd-Z superheavy isotopes.
Worldwide dubnium production is measured in single atoms per synthesis event, with successful experiments producing perhaps 1-5 atoms per hour during optimal runs. Global annual production totals fewer than thousands of atoms across all facilities.
Unlike elements formed through stellar nucleosynthesis, supernovae, or cosmic ray interactions, no dubnium survives in nature because of its short half-lives, and whether the r-process in neutron star mergers briefly makes it is an open question. Every known dubnium atom was made in a laboratory.
Handling
Dubnium is radioactive. It has no stable isotope — every nucleus decays. Handling requires appropriate shielding and licensing.
Dubnium is radioactive, but it is made only a few atoms at a time in heavy-ion accelerators. Its isotopes decay by spontaneous fission, alpha emission and electron capture; the longest-lived, dubnium-268, has a half-life of about 28 hours. No weighable amount of dubnium has ever existed, so the atoms themselves cannot deliver a meaningful radiation dose to anyone.
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. They are controlled by shielding and remote handling, and the waste 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. 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
Dubnium (symbol Db) is element 105 on the periodic table, a transition metal in period 7, group 5. Named after Dubna, the Russian town where much of superheavy chemistry was pioneered. At room temperature it is a solid, and it is radioactive.
[Rn] 5f¹⁴ 6d³ 7s², giving 7 occupied shells with the distribution 2, 8, 18, 32, 32, 11, 2.Dubnium has no stable isotope, so it has no standard atomic weight. The figure quoted, 268, is the mass number of its longest-lived known isotope.
Dubnium has no stable isotope. Its longest-lived known isotope, Db-268, has 163 neutrons (mass number 268 minus atomic number 105) and a half-life of 28 hr. The classroom shortcut, rounded atomic mass (268) minus atomic number, gives the same 163.
Dubnium is predicted to have a density of about 29.3 g/cm³, though no sample large enough to weigh has ever been made. Water is 1.0 g/cm³ for comparison.
Dubnium was discovered in 1967 by JINR Dubna & Berkeley. Origin of the name: Dubna, Russia.
Dubnium does not occur naturally on Earth in any meaningful quantity — it is made in a reactor or an accelerator.
Yes. Dubnium has no stable isotope — every one of its nuclei decays. It does not occur in usable quantities in nature and must be synthesised.