Dubnium

Dubnium is a synthetic chemical element; it has symbol Db and atomic number 105. It is highly radioactive: the most stable known isotope, dubnium-268, has a half-life of about 16 hours. This greatly limits extended research on the element.

"Hahnium" redirects here. Not to be confused with Hafnium.

Dubnium, 105Db
Dubnium
Pronunciation
  • /ˈduːbniəm/
    (DOOB-nee-əm)
  • /ˈdʌbniəm/
    (DUB-nee-əm)
Mass number[268]
Dubnium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
 Ta
↑
Db
↓
(Upe)
rutherfordium ← dubnium → seaborgium
Atomic number (Z)105
Groupgroup 5
Periodperiod 7
Block  d-block
Electron configuration[Rn] 5f14 6d3 7s2
Electrons per shell2, 8, 18, 32, 32, 11, 2
Physical properties
Phase at STPsolid (predicted)
Density (near r.t.)21.6 g/cm3 (predicted)
Atomic properties
Oxidation states(+3), (+4), +5 (parenthesized: prediction)
Ionization energies
  • 1st: 665 kJ/mol
  • 2nd: 1547 kJ/mol
  • 3rd: 2378 kJ/mol
  • (more) (all but first estimated)
Atomic radiusempirical: 139 pm (estimated)
Covalent radius149 pm (estimated)
Other properties
Natural occurrencesynthetic
Crystal structure ​body-centered cubic (bcc) (predicted)
CAS Number53850-35-4
History
Namingafter Dubna, Moscow Oblast, Russia, site of Joint Institute for Nuclear Research
Discoveryindependently by the Lawrence Berkeley Laboratory and the Joint Institute for Nuclear Research (1970)
Isotopes of dubnium
Main isotopes Decay
abun­dance half-life (t1/2) mode pro­duct
262Db synth 34 s α67% 258Lr
SF33% –
263Db synth 27 s SF56% –
α41% 259Lr
ε3% 263mRf
266Db synth 11 min SF –
ε 266Rf
267Db synth 1.4 h SF –
268Db synth 16 h SF –
ε 268Rf
α 264Lr
270Db synth 1 h SF17% –
α83% 266Lr

Dubnium does not occur naturally on Earth and is produced artificially. The Soviet Joint Institute for Nuclear Research (JINR) claimed the first discovery of the element in 1968, followed by the American Lawrence Berkeley Laboratory in 1970. Both teams proposed their names for the new element and used them without formal approval. The long-standing dispute was resolved in 1993 by an official investigation of the discovery claims by the Transfermium Working Group, formed by the International Union of Pure and Applied Chemistry and the International Union of Pure and Applied Physics, resulting in credit for the discovery being officially shared between both teams. The element was formally named dubnium in 1997 after the town of Dubna, the site of the JINR.

Theoretical research establishes dubnium as a member of group 5 in the 6d series of transition metals, placing it under vanadium, niobium, and tantalum. Dubnium should share most properties, such as its valence electron configuration and having a dominant +5 oxidation state, with the other group 5 elements, with a few anomalies due to relativistic effects. A limited investigation of dubnium chemistry has confirmed this.

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