Dubnium
Transition metal · Period 7 · Group 5 · d-block
Named for a Russian science city after decades of dispute
- Atomic mass
- 268 u
- State at 25 °C
- Solid
- Electronegativity
- —
- Melting point
- —
- Boiling point
- —
- Configuration
- *[Rn] 5f14 6d3 7s2
Nucleus drawn at reduced count for clarity. Drag to rotate.
Dubnium, explained
Video lesson in production
Bhavya’s explainer for this element will play here.
Overview
Dubnium sits in group 5 of the periodic table, below vanadium, niobium and tantalum, with a predicted 7s2 6d3 configuration. Experiments confirm its highest and most stable oxidation state is +5, like its lighter group members. Gas-phase studies show it forms volatile halides and oxyhalides, and aqueous studies show it forms fluoride and chloride complexes. In some extraction systems dubnium behaves more like niobium or protactinium than like tantalum, the element directly above it.
Those deviations are what make dubnium worth studying. Relativistic effects alter the energies of its 7s and 6d orbitals, so simple extrapolation down the group does not predict its chemistry exactly. Dubnium-268, the longest-lived known isotope, has a half-life of about 16 hours, remarkably long for a superheavy element. It was first observed in 2004 as the end of a decay chain starting from moscovium, element 115.
Discovery
Georgy Flerov's group at Dubna reported element 105 in 1968 and 1970 by bombarding americium-243 with neon-22; Albert Ghiorso's group at Berkeley made it in 1970 from californium-249 and nitrogen-15. The Soviets proposed nielsbohrium and the Americans hahnium, after Otto Hahn. In 1997 IUPAC named it dubnium after Dubna, the town north of Moscow where the Joint Institute for Nuclear Research stands, and credited both laboratories.
- Where it’s found
- Dubnium does not occur in nature; it is made in accelerators or forms as a decay product of heavier synthetic elements.
- What it’s used for
- Group 5 chemistry studies
- Relativistic effects research
- Decay-chain identification
- Nuclear structure research
- In living things
- Dubnium has no biological role; it is radioactive and has only ever existed as individual atoms.
- Safety
- Radioactive and made only a few atoms at a time; it poses no hazard outside the experiment.
How it compares
Where Dubnium sits among all 118 elements on the trends that shape the table.
- ElectronegativityNo data
Not measured for this element
- Ionization energyNo data
Not measured for this element
- Atomic radiusNo data
Not measured for this element
- Electron affinityNo data
Not measured for this element
- Density29.3g/cm³
#6 of 114 elements with data · predicted
- Melting pointNo data
Not measured for this element
- Density
- 29.3 g/cm³
- Atomic radius
- —
- Covalent radius
- —
- Molar heat
- —
- Appearance
- —
- Discovered by
- Joint Institute for Nuclear Research
Inside the atom
105 electrons arranged in 7 shells: 2 · 8 · 18 · 32 · 32 · 11 · 2.
Orbital diagram
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d3 · shorthand *[Rn] 5f14 6d3 7s2
- 1s2
- 2s2
- 2p6
- 3s2
- 3p6
- 4s2
- 3d10
- 4p6
- 5s2
- 4d10
- 5p6
- 6s2
- 4f14
- 5d10
- 6p6
- 7s2
- 5f14
- 6d3
Each box is an orbital holding up to two electrons of opposite spin. Highlighted subshells hold the valence electrons that decide how Dubnium bonds.
Signature reactions
How the first atoms were made, and how they fall apart.
Nuclear · Fusion-evaporation
Berkeley synthesis
Nitrogen-15 fuses with californium-249 and four neutrons evaporate from the compound nucleus. Ghiorso's group tied the alpha decays of dubnium-260 to its known lawrencium-256 daughter.
Conditions: nitrogen-15 beam on californium-249, Berkeley HILAC, 1970
Nuclear · Fusion-evaporation
Dubna synthesis
Neon-22 fuses with americium-243 and the compound nucleus loses four neutrons. Dubna detected alpha activity and spontaneous fission from dubnium isotopes made this way.
Conditions: neon-22 beam on americium-243, Dubna, 1968-1970
Synthesis · Gas-phase chlorination
Formation of dubnium pentachloride
Dubnium atoms carried into a chlorinating gas form a volatile chloride; with traces of oxygen present the oxychloride DbOCl3 forms instead. Comparing their volatility with niobium and tantalum compounds confirmed dubnium as a group 5 element with its own relativistic quirks.
Conditions: single atoms in a chlorinating gas stream, thermochromatography
Where you’ll meet it
Dubna
The science town on the Volga north of Moscow gives element 105 its name.
Photo: Wikimedia Commons
Joint Institute for Nuclear Research
Dubna's institute has been involved in discovering more superheavy elements than any other lab.
Photo: Wikimedia Commons
Otto Hahn
Berkeley wanted to name element 105 hahnium after this co-discoverer of nuclear fission.
Photo: Wikimedia Commons
Niobium
Dubnium's group 5 chemistry is benchmarked against niobium, which it sometimes resembles more than tantalum.
Photo: Wikimedia Commons
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Research
No research on Dubnium yet
When Bhavya publishes a project that studies Dubnium, it will be linked here.