Periodic Table of Elements




Dubnium was first discovered in 1968 at the Joint Institute for Nuclear Research at Dubna, Russia. Researchers there bombarded an americium-243 target with neon-22 ions.

Name: Dubnium
Symbol: Db
Atomic number: 105
Atomic weight: 268.13
State: solid presumably
Group, period, block: 5, 7, d
Color: unknown
Classification: transition metal
Electron configuration: 5f14 6d3 7s2

Physical properties

Density: 29 g/cm-3
Melting point: 302.9146 K, 29.7646 C, 85.5763 F
Boiling point: 2477 K, 2204 C, 3999 F

Atomic properties

Oxidation states: 5, 4, 3
Electronegativity: no data
Ionization energies: 1st: 664.8 kJmol-1
Covalent radius: 149 pm
Van der Waals radius: no data
  • Db
  • Electron Configuration


Dubnium is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was 261Db in 1968. There are 12 known radioisotopes from 256Db to 270Db, and 1-3 isomers. The longest-lived isotope is 268Db with a half-life of 32 hours.