Dubnium
Dubnium is a chemical element with symbol Db and atomic number 105. It is named after the town of Dubna in Russia (north of Moscow), where it was first produced. It is a synthetic element (an element that can be created in a laboratory but is not found in nature) and radioactive; the most stable known isotope, dubnium-268, has a half-life of approximately 28 hours.
Identity
- Atomic mass
- [268] u
- Category
- Transition metals
- Group
- 5
- Period
- 7
- Block
- d
- Oxidation States
- +5
- Phase (25 °C)
- Solid
Electronic Structure
- Electron configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d3
- Short configuration
- *[Rn] 5f14 6d3 7s2
- Electrons per shell
- 2, 8, 18, 32, 32, 11, 2
- Electronegativity (Pauling)
- —
- Electron affinity
- —
- 1st ionization energy
- —
Physical properties
- Melting point
- —
- Boiling point
- —
- Density
- 29.3 g/cm³
- Molar heat capacity
- —
Chemical behavior of dubnium
Dubnium is a superheavy transactinide with symbol Db and atomic number 105, located in group 5 below tantalum. Its calculated electron configuration is [Rn] 5f¹⁴ 6d³ 7s². It presents the characteristic oxidation state of +5 (Db⁵⁺), forming volatile halides and very stable oxycomplexes. Due to intense relativistic effects on its 7s and 6d orbitals, theoretical models and single-atom tests reveal that its chemical properties subtly diverge from those of niobium and tantalum, approaching in certain hydrolysis and solvent extraction aspects protactinium.
Reactivity
Db + 5 HCl → DbCl₅ + 5/2 H₂ (predicted)
It forms volatile dubnium pentachloride when reacting with chlorinating agents in the gas phase in thermochromatographic systems.
DbCl₅ + H₂O → DbOCl₃ + 2 HCl
In the presence of traces of humidity or water vapor it forms dubnium oxychloride, analogous to niobium oxychloride.
Db⁵⁺ + 6 HF → [DbF₆]⁻ + H⁺
In aqueous hydrofluoric acid solutions it generates anionic hexafluoro and heptafluoro complexes on ion-exchange resins.
Notable compounds
| Compound | Formula | Use or importance |
|---|---|---|
| Dubnium pentachloride | DbCl₅ | Volatile gaseous halide characterized in adsorption experiments to determine its sublimation enthalpy |
| Dubnium oxychloride | DbOCl₃ | Oxyhalogenated compound observed in gas thermochromatography coupled to online nuclear separators |
| Potassium hexafluorodubniate | K[DbF₆] | Aqueous-phase dubnium anionic complex studied to compare its ionic affinity against tantalum and niobium |
Electron shell distribution
View in the atom builderIsotopes
All known dubnium isotopes are radioactive and produced by nuclear synthesis. Thirteen isotopes are known with masses between 255 and 270. Particularly notable is dubnium-268 (²⁶⁸Db), which has an extraordinarily prolonged half-life for a transactinide of approximately 28 to 30 hours, decaying by spontaneous fission or electron capture. Other isotopes crucial in chemical research are dubnium-262 (²⁶²Db, half-life of 34 seconds) and dubnium-263 (²⁶³Db, half-life of 27 seconds).
Occurrence and production
An artificial element with no natural presence on Earth. Its synthesis is carried out in heavy-ion accelerators bombarding americium-243 targets with neon-22 ions or by bombarding berkelium-249 with oxygen-18 nuclei. Likewise, dubnium-268 is generated naturally in laboratories as the terminal product of successive alpha decay chains of superheavy elements such as moscovium and nihonium.
History and origin of the name
Element 105 was first produced in 1968 at the Dubna Institute (Russia) under the direction of Georgy Flyorov, and confirmed in 1970 by Albert Ghiorso's team at the Lawrence Berkeley Laboratory (USA). The Soviet team proposed naming it 'nielsbohrium' (Ns) in honor of Niels Bohr, while the American team proposed 'hahnium' (Ha) in honor of nuclear fission discoverer Otto Hahn. In 1997, IUPAC settled the dispute officially assigning the name 'dubnium' in honor of the Russian scientific city of Dubna.
Applications and relevance of dubnium
Uses of the element
It has no commercial, industrial or technological applications. It is used exclusively in theoretical and experimental nuclear physics to understand neutron nuclear shell structure and in single-atom radiochemical analysis to unravel how relativistic effects modify the periodicity of group 5 metals.
Uses of its compounds
Dubnium halogenated compounds are synthesized only as transient chemical species in vapor phase for gas chromatography and automated liquid-liquid extraction experiments.
Health, safety and environment
Biological role
It has no physiological role in nature. No living organism comes into contact with it since it is produced atom by atom in highly shielded scientific facilities.
Safety
The direct radiological risk is limited to the vicinity of the cyclotron and to the heavy transuranium actinide targets used for its production.
Environment
It generates no environmental pollution nor ecological waste since its atoms are produced in nanoscopic quantities that decay completely in a short time.
Frequently asked questions about Dubnium
Why does dubnium-268 have one of the longest half-lives among superheavy elements?
Most superheavy nuclides decay in fractions of a second. However, dubnium-268 contains one hundred sixty-three neutrons, approaching the deformed magic nucleon shell N=162. This nuclear quantum symmetry strongly stabilizes the nucleus against spontaneous fission, extending its half-life to nearly thirty hours. Its prolonged survival makes it the ideal nuclide for complex dissolution and aqueous separation chemical experiments.
How is a dubnium atom transported from the accelerator to the analysis equipment?
When a dubnium atom is formed in an accelerator, it must be taken rapidly to the measuring apparatus before it decays. For this, a gas stream can drag the atoms to the analysis zone. There its chemical behavior is studied or its radioactive decay is recorded. The system must work fast because only minuscule quantities are produced.
How do relativistic effects influence the volatility of dubnium chlorides in the gas phase?
Relativistic quantum chemistry calculations predicted that dubnium pentachloride (DbCl₅) would be considerably less volatile than tantalum or niobium pentachloride due to 7s orbital contraction and the higher polarizability of the heavy atom. Thermochromatography experiments in quartz columns confirmed that dubnium chloride condenses at higher temperatures than its lighter homologues, validating that relativistic effects modify intermolecular bonding forces.
What is needed to manufacture dubnium in a laboratory?
To produce dubnium an accelerator is needed that directs atomic nuclei against a target of another element. If the nuclei fuse, a dubnium nucleus may form, but the probability is very low. The experiments require intense beams, precisely prepared targets and sensitive detectors that identify subsequent decays. Even in specialized facilities, only minuscule quantities are obtained.
Why did dubnium surprise chemists when studying its reactions?
According to the usual periodic table rule, an element should resemble the one just above it (tantalum) more. However, in the first chemical experiments with individual dubnium atoms in solution, it was discovered that its ions behaved more like niobium. The relativistic attraction of its enormous nucleus changes the position of its outer electrons, modifying its chemical preferences.
How does the automated liquid-liquid extraction technique work to study a single dubnium atom?
The automated SISAK system collects the dubnium atom expelled from the accelerator and dissolves it in a continuous stream of aqueous acid. In high-speed liquid microcentrifuges, the aqueous phase is intimately mixed for one second with an immiscible organic solvent containing extractants such as amines or crown ethers. Separating the two phases at supersonic speed, liquid scintillation detectors determine in which of the two phases the individual dubnium atom migrated.
Why is dubnium-268 the final decay product in superheavy element chains?
When odd superheavy elements such as moscovium-288 (115) or nihonium-284 (113) are synthesized in collisions with calcium-48, these nuclei lose alpha particles successively in a chain decay cascade. After four or five consecutive alpha emissions, the chain stops at dubnium-268, which has a half-life of more than one day. The unequivocal identification of dubnium-268 and its final fission demonstrates the creation of the progenitor elements.
Main sources consulted: PubChem, Royal Society of Chemistry, NIST, IUPAC. Last revision: November 2026.