# Dubnium
**Dubnium** is a synthetic chemical element with symbol Db and atomic number 105, classified as a transition metal in group 5 of the periodic table and expected to be a solid at room temperature.[1](https://pubchem.ncbi.nlm.nih.gov/element/105) It does not occur naturally in the [Earth's crust](https://www.edgepedia.org/earths-crust) and is produced only in particle accelerators, one atom at a time.[1](https://pubchem.ncbi.nlm.nih.gov/element/105) • [2](https://periodic-table.rsc.org/element/105/Dubnium) Its most stable isotope, dubnium-268, has a half-life of about 32 hours and decays through spontaneous fission.[1](https://pubchem.ncbi.nlm.nih.gov/element/105)
| Key fact | Detail |
|---|---|
| Identity | Element 105, symbol Db, group 5, period 7, d-block; solid at 25 °C[1](https://pubchem.ncbi.nlm.nih.gov/element/105) • [2](https://periodic-table.rsc.org/element/105/Dubnium) |
| Electron configuration | [Rn] 5f14 6d3 7s2; oxidation states 5, 4, 3[1](https://pubchem.ncbi.nlm.nih.gov/element/105) • [2](https://periodic-table.rsc.org/element/105/Dubnium) |
| Longest-lived isotope | 268Db, half-life about 32 hours, decays by spontaneous fission[1](https://pubchem.ncbi.nlm.nih.gov/element/105) |
| First reports | Dubna (Flerov team) 1967–1968, 243Am + 22Ne; Berkeley (Ghiorso team) 1970, 249Cf + 15N[1](https://pubchem.ncbi.nlm.nih.gov/element/105) • [3](https://publications.iupac.org/news/archives/1997/august97.html) |
| Name | Dubnium, after the Joint Institute for Nuclear Research in Dubna, Russia; adopted by IUPAC in 1997[3](https://publications.iupac.org/news/archives/1997/august97.html) |
| Uses | None outside basic scientific research, because of tiny production amounts and short half-life[1](https://pubchem.ncbi.nlm.nih.gov/element/105) |
| Chemical homologs | Niobium (Nb) and tantalum (Ta)[4](https://rdreview.jaea.go.jp/review_en/2022/e2022_3_1.html) |
## Discovery and the naming dispute
Scientists at the [Joint Institute for Nuclear Research](https://www.edgepedia.org/joint-institute-for-nuclear-research) (JINR) in Dubna, Russia, first reported the production of element 105 in 1967, bombarding atoms of americium-243 with ions of neon-22 to form atoms of dubnium-260 and dubnium-261; the evidence was based on time-coincidence measurements of alpha energies.[1](https://pubchem.ncbi.nlm.nih.gov/element/105) In 1970, a team led by [Albert Ghiorso](https://www.edgepedia.org/albert-ghiorso) at the Lawrence Radiation Laboratory (now Lawrence Berkeley Laboratory) in California bombarded californium-249 with 84 MeV nitrogen-15 ions in the Heavy Ion Linear Accelerator (HILAC), producing dubnium-260 with a half-life of 1.6 seconds; the first atoms were detected conclusively on March 5, 1970.[1](https://pubchem.ncbi.nlm.nih.gov/element/105) Credit for the discovery was disputed between the two laboratories, and Ghiorso's group attempted to confirm the Soviet findings by more sophisticated methods without success.[1](https://pubchem.ncbi.nlm.nih.gov/element/105)
The two groups gave the element different names. The Berkeley team proposed hahnium (symbol Ha), after the German chemist [Otto Hahn](https://www.edgepedia.org/otto-hahn), while the Russian team used nielsbohrium.[1](https://pubchem.ncbi.nlm.nih.gov/element/105) • [2](https://periodic-table.rsc.org/element/105/Dubnium) The dispute was part of the wider "Transfermium Wars" over elements 104 to 106, contested between Berkeley and Dubna during the Cold War.[5](https://www.sciencehistory.org/stories/magazine/the-transfermium-wars-scientific-brawling-and-name-calling-during-the-cold-war/) In 1997, IUPAC's Committee on Nomenclature of Inorganic Chemistry accepted the name dubnium in honor of the Dubna laboratory, where important contributions to the creation of transfermium elements originated; the Council approved the final names for elements 101 to 109 by a vote of 64 to 5.[3](https://publications.iupac.org/news/archives/1997/august97.html) The commission noted that both laboratories had made significant contributions and that Dubna had played a key role in developing the experimental strategies used to synthesize several transfermium elements.[6](https://media.iupac.org/reports/1997/6912transfermium/index.html) Because dubnium was chosen for element 105, the name hahnium cannot be used for another as-yet-unnamed element.[7](https://media.iupac.org/publications/pac/2002/pdf/7405x0787.pdf)
## Isotopes and nuclear properties
Dubnium has no stable isotopes.[8](https://linelist.pa.uky.edu/newpage/content/elm105.html) Thirteen radioisotopes have been characterized, ranging from 255Db to 270Db.[9](https://www.chemlin.org/chemical-elements/dubnium-isotopes.php) Half-lives span from milliseconds to hours: 260Db decays with a half-life of 1.52 seconds, 262Db in about 35 seconds, 267Db in 73 minutes, and 268Db in about 32 hours, the longest known.[8](https://linelist.pa.uky.edu/newpage/content/elm105.html) The decay modes vary with mass number: lighter isotopes such as 260Db and 261Db decay mainly by alpha emission, while 267Db and 268Db decay by spontaneous fission.[10](https://stem-tools.jlab.org/itselemental/iso105) The relative atomic mass of the most stable isotope is 268.12567(57) u.[8](https://linelist.pa.uky.edu/newpage/content/elm105.html)
The stability of the neutron-rich isotope 268Db, which has a neutron number of 163, is influenced by the closed neutron shell at N = 162.[11](https://publications.iupac.org/pac/pdf/2006/pdf/7805x0889.pdf)
## Chemistry at the edge of the periodic table
As a group 5 element, dubnium is the chemical homolog of niobium and tantalum, and its predicted electronic configuration suggests a maximum oxidation state of +5, with stable pentahalides and oxyhalides expected.[4](https://rdreview.jaea.go.jp/review_en/2022/e2022_3_1.html) • [12](https://pmc.ncbi.nlm.nih.gov/articles/PMC8456785/) Because production rates are extremely low, about one atom per five minutes for the reactions used in chemical studies, and half-lives are short (34 seconds for 262Db), only one atom can be used at a time.[4](https://rdreview.jaea.go.jp/review_en/2022/e2022_3_1.html) Chemical experiments therefore rely on repeated single-atom partition measurements, with gas chromatography the preferred method for nuclides with half-lives of a few seconds.[12](https://pmc.ncbi.nlm.nih.gov/articles/PMC8456785/)
**Relativistic effects.** In superheavy elements, the inner electrons move at speeds approaching that of light, which alters the outer electron orbits that determine chemical behavior; the chemical properties of superheavy elements may therefore differ from what the periodic table alone predicts.[4](https://rdreview.jaea.go.jp/review_en/2022/e2022_3_1.html) A 2021 study at the Japan Atomic Energy Agency synthesized the volatile oxychloride DbOCl3 in situ by reacting 262Db atoms with thionyl chloride vapor in a quartz column held at 1000 °C, then measured its adsorption on quartz by isothermal gas chromatography over 350 to 600 °C.[13](https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202102808) Twenty-four correlated alpha-decay chains attributed to 262Db → 258Lr → 254Md were detected, and the adsorption enthalpy was determined as −ΔHads(DbOCl3) = 130 ± 6 kJ/mol.[13](https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202102808) From this, the sublimation enthalpy of the compound was estimated at 172 ± 10 kJ/mol, and the volatility sequence along the group 5 oxychlorides was found to be NbOCl3 > TaOCl3 ≥ DbOCl3.[13](https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202102808) The volatility of DbOCl3 proved comparable to that of the tantalum compound, though simple extrapolation of the periodic table predicted it to be lower; this unexpected result is explained by strong relativistic effects.[4](https://rdreview.jaea.go.jp/review_en/2022/e2022_3_1.html) • [13](https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202102808) The same study inferred a standard sublimation enthalpy of metallic dubnium of 792 ± 10 kJ/mol, close to the extrapolated value of 795 kJ/mol, indicating that dubnium is among the least volatile of the transactinides together with seaborgium and bohrium.[13](https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202102808)
## Physical description and uses
Dubnium is a highly radioactive metal of which only a few atoms have ever been made; no macroscopic sample exists, so bulk properties such as density, melting point, and boiling point are not established experimentally.[2](https://periodic-table.rsc.org/element/105/Dubnium) • [14](https://www.mendeleev.com/elements/dubnium.html) It has no known biological role.[2](https://periodic-table.rsc.org/element/105/Dubnium) Due to the small amounts produced and the short half-life, there are currently no uses for dubnium outside basic scientific research.[1](https://pubchem.ncbi.nlm.nih.gov/element/105)
## References
1. [Dubnium | Db (Element), PubChem](https://pubchem.ncbi.nlm.nih.gov/element/105)
2. [Dubnium, Royal Society of Chemistry Periodic Table](https://periodic-table.rsc.org/element/105/Dubnium)
3. [IUPAC Adopts Final Recommendations for Names of Transfermium Elements (August 30, 1997)](https://publications.iupac.org/news/archives/1997/august97.html)
4. [What is the Chemical Behavior of the Heaviest Element? JAEA R&D Review 2022-23](https://rdreview.jaea.go.jp/review_en/2022/e2022_3_1.html)
5. [The Transfermium Wars, Science History Institute](https://www.sciencehistory.org/stories/magazine/the-transfermium-wars-scientific-brawling-and-name-calling-during-the-cold-war/)
6. [Names and Symbols of Transfermium Elements (IUPAC Recommendations 1997)](https://media.iupac.org/reports/1997/6912transfermium/index.html)
7. [IUPAC 2002 report on naming procedures, Pure Appl. Chem. 74, 787](https://media.iupac.org/publications/pac/2002/pdf/7405x0787.pdf)
8. [Dubnium, Atomic Line List](https://linelist.pa.uky.edu/newpage/content/elm105.html)
9. [Dubnium Isotopes, List and Properties, ChemLin](https://www.chemlin.org/chemical-elements/dubnium-isotopes.php)
10. [It's Elemental: Isotopes of Dubnium, Jefferson Lab](https://stem-tools.jlab.org/itselemental/iso105)
11. [IUPAC 2006, Pure Appl. Chem. 78, 889](https://publications.iupac.org/pac/pdf/2006/pdf/7805x0889.pdf)
12. [Chemical Characterization of a Volatile Dubnium Compound, DbOCl3 (PMC version)](https://pmc.ncbi.nlm.nih.gov/articles/PMC8456785/)
13. [Chiera et al. (2021), Angewandte Chemie International Edition](https://onlinelibrary.wiley.com/doi/full/10.1002/anie.202102808)
14. [Dubnium (Db), Mendeleev](https://www.mendeleev.com/elements/dubnium.html)
---
*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Elements and inorganic substances › Element classifications and synthetic elements › Extended, synthetic, and hypothetical elements › Overview of synthetic and superheavy elements*
*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license