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Name , symbol , atomic number Dubnium, Db, 105
Element category Transition metals
Group , period , block 5 , 7 , d
CAS number 53850-35-4
EC number 611-058-7
ECHA InfoCard 100.126.367
Atomic mass 262,1138 u
Electron configuration [ Rn ] 5 f 14 6 d 3 7 s 2 (?)
1. Ionization energy 6th.8 (5) eV656 kJ / mol
2. Ionization energy 14th.0 (1.6) eV1 350 kJ / mol
3. Ionization energy 23.1 (1.6 eV)2 230 kJ / mol
4. Ionization energy 33.0 (1.7) eV3 180 kJ / mol
5. Ionization energy 43.0 (1.9 eV)4 150 kJ / mol
isotope NH t 1/2 ZA ZE (M eV ) ZP
261 Db {syn.} 1.8 s α 9.270 257 Lr
262 Db {syn.} 34 p α 9.210 258 Lr
ε 4,000 262 Rf
263 Db {syn.} 27 p SF    
α 9.030 259 Lr
268 Db {syn.} 16 h SF    
For other isotopes see list of isotopes
Hazard and safety information
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used.
Unless otherwise noted, the data given apply to standard conditions .

Dubnium (formerly also: Hahnium , Nielsbohrium ) is an exclusively artificially produced chemical element with the element symbol Db and the atomic number 105. It is one of the transactinoids . In the periodic table of the elements it is in the 5th  IUPAC group , the vanadium group . All Dubnium isotopes are radioactive .


Georgi N. Flerow , discoverer of Dubnium in 1967, on a special Russian stamp on the occasion of his 100th birthday (2013)
Albert Ghiorso, discoverer of Dubnium in 1970

Dubnium was discovered in 1967 by Georgi N. Flerow et al. at the United Institute for Nuclear Research at Dubna near Moscow and in 1970 by Albert Ghiorso et al. at the University of California , Berkeley . Like all transactinoids , Dubnium is artificially produced exclusively by particle bombardment. The Soviet working group worked with the bombardment of americium by neon cores and suggested the name Nielsbohrium for it:

The American team, on the other hand, shot at Californium or Berkelium with nitrogen or oxygen nuclei and gave the resulting element the name Hahnium :

After an element naming controversy , it was named after the Russian nuclear research center Dubna in 1997 . Other names that were used at times for this element were:


So far, the element has only been synthesized in very small quantities for research purposes (in the experiments of Albert Ghiorso et al., For example, about 6 atoms per hour were produced) and has so far not been of any significance.

Web links

Commons : Dubnium  - collection of images, videos and audio files
Wiktionary: Dubnium  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. a b c d e Entry on dubnium in Kramida, A., Ralchenko, Yu., Reader, J. and NIST ASD Team (2019): NIST Atomic Spectra Database (ver. 5.7.1) . Ed .: NIST , Gaithersburg, MD. doi : 10.18434 / T4W30F ( https://physics.nist.gov/asd ). Retrieved June 13, 2020.
  2. a b c d e Entry on dubnium at WebElements, https://www.webelements.com , accessed on June 13, 2020.
  3. The hazards emanating from radioactivity do not belong to the properties to be classified according to the GHS labeling. With regard to other hazards, this element has either not yet been classified or a reliable and citable source has not yet been found.
  4. Albert Ghiorso, Matti Nurmia, Kari Eskola, James Harris, Pirkko Eskola: New Element Hahnium, atomic number 105. In: Physical Review Letters , 1970 , 24  (26), pp 1498-1503; doi : 10.1103 / PhysRevLett.24.1498 .
  5. ^ Entry on Dubnium. In: Römpp Online . Georg Thieme Verlag, accessed on August 3, 2020.