Dubnium (Db)

Dubnium is named after the Joint Institute for Nuclear Research at Dubna, north of Moscow, which is the only laboratory to have had a hand in discovering more than a handful of elements — Dubna's collaborations account for flerovium, moscovium, livermorium, tennessine and oganesson as well. The name was the compromise that ended the Transfermium Wars: Dubna gave up its claim to element 104, and got 105. Chemistry on a few atoms has confirmed it behaves as a group 5 element, though not quite as much like tantalum as simple extrapolation predicts.

Properties

Atomic number

105

Symbol

Db

Mass number of most stable isotope

[268]

Category

Transition metal

Group

5

Period

7

Block

d-block

Electron configuration

[Rn] 7s² 5f¹⁴ 6d³

Electrons per shell

2, 8, 18, 32, 32, 11, 2

Oxidation states

+5, +4, +3

Discovered

1968 by Dubna, with independent work at Berkeley in 1970; IUPAC credited both

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f¹⁴ 6d³

Noble gas shorthand

[Rn] 7s² 5f¹⁴ 6d³

Shells

K: 2 · L: 8 · M: 18 · N: 32 · O: 32 · P: 11 · Q: 2

What it is used for

• Research only; no application outside the laboratory

Hazards

• Intensely radioactive; exists only as individual atoms in an accelerator

Melting point, boiling point, density and electronegativity are omitted: no measurement is possible. The mass given is the mass number of dubnium-268, the longest-lived at roughly 28 hours.

Several physical properties are not listed for dubnium because no bulk sample has ever existed. Only a handful of atoms have been produced, often with half-lives measured in seconds, so published melting points and densities for elements in this range are calculations rather than measurements. They are omitted rather than presented as observed values.

Neighbours in the table

Group 5

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Dubnium sits in group 5 with vanadium, niobium, tantalum.