Atomic number 105 · Transition metal
Dubnium Db
Dubnium is a superheavy element named after Dubna, the Russian science town that has produced many new elements. Like rutherfordium it was fought over by American and Soviet laboratories, and on its way to its final name it was called nielsbohrium, hahnium and joliotium. Unusually for a superheavy element, one of its isotopes survives for most of a day.
Key properties
| Atomic number | 105 |
|---|---|
| Atomic weight | [268] (No stable isotope; mass number of a representative isotope in brackets) |
| Category | Transition metal |
| Group | 5 |
| Period | 7 |
| Block | d |
| State (25 °C, 1 atm) | Solid |
| Melting point | — |
| Boiling point | — |
| Density | — |
| Electronegativity (Pauling) | — |
| Atomic radius (van der Waals) | — |
| First ionization energy | — |
| Electron affinity | — |
| Oxidation states | 5, 4, 3 |
| Discovered | 1967 |
Electron configuration
- Condensed
- [Rn]7s2 5f14 6d3
- Full
- 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f14 6s2 6p6 6d3 7s2
- Electrons per shell
- 2 · 8 · 18 · 32 · 32 · 11 · 2
Orbital diagram
Position in the table
Discovery
In 1968 Flerov's group at Dubna reported signs of element 105 from bombarding americium-243 with neon-22 ions, publishing fuller results in 1970. In the same year, 1970, Ghiorso's team at Berkeley announced dubnium-260 made by firing nitrogen-15 ions at californium-249.
The names diverged too. The Soviets used 'nielsbohrium' (Ns) for Niels Bohr; the Americans used 'hahnium' (Ha) for Otto Hahn. In 1992 the joint working group credited both teams. In 1994 IUPAC proposed 'joliotium', after Frédéric Joliot-Curie, which proved unpopular. In the final compromise of 1997, element 105 became dubnium in recognition of the Dubna laboratory's contributions.
Origin of the name
The element takes its name from Dubna, a science town north of Moscow and home of the Joint Institute for Nuclear Research, where many superheavy elements were first made. The symbol is Db. Like berkelium, it honours a research town.
Main uses
- Basic research: It has no uses outside science.
- Chemistry: Dubnium is expected to resemble niobium and tantalum in group 5, and single-atom experiments have compared it with them. Some results hinted at small departures from the trend of its lighter relatives, discussed in connection with relativistic effects.
Isotopes
There are no stable isotopes. The longest-lived, dubnium-268, has a half-life of about 16 hours, one of the longest among superheavy nuclei. It was first identified at the end of the decay chain of element 115, moscovium. Dubnium-260, the isotope reported by Berkeley, has a half-life of about 1.5 seconds.
In everyday life
It does not exist in nature; only a few atoms at a time are made in accelerators and they decay almost immediately, so it has no connection with daily life or health.
Good to know
- Element 105 passed through the names nielsbohrium, hahnium and joliotium before becoming dubnium.
- Dubnium-268 has a half-life of about 16 hours.
- Dubnium-268 was found as the end product of several successive decays of element 115.
Same group (5)
Data sources · Properties: PubChem Periodic Table (US NIH/NLM public data) · Atomic weights: CIAAW 2024 abridged standard atomic weights · Names: Wikidata (CC0); Korean names follow the Korean Chemical Society. Retrieved 2026-09-23.