Dubnium (Db)

Dubnium is a radioactive chemical element with an atomic number of 105 in the periodic table. It’s not found in Earth’s crust since it’s a synthetically produced element. Being a member of the transuranium element family, dubnium is expected to have five valence electrons.

Chemical and Physical Properties of Dubnium

The symbol in the periodic table of elements
Atomic number105
Atomic weight (mass)261.9 g.mol -1
Group number5 (Transactinoids)
Physical stateSolid at 20°C
Half-lifeFrom 37(+51-14) ms to 29 hours
Electronegativity according to PaulingN/A
Density21.6 g/cm3 (Predicted)
Melting pointN/A
Boiling pointN/A
Van der Waals radiusN/A
Ionic radiusN/A
Most characteristic isotope268Db
Electronic shell[Rn] 5f146d37s2
The energy of the first ionizationN/A
The energy of the second ionizationN/A
Discovery dateIn 1968-1970 by Albert Ghiorso, USA, and Georgy. N. Flerov, Russia

Dubnium is a man-made highly radioactive and unstable element with the periodic table symbol Db, atomic number 105, atomic mass of 261.9 g.mol-1, an estimated atomic radius of 139 pm, and electron configuration of [Rn] 5f146d37s2.

This extremely heavy transactinide element supposedly resembles the properties of the transition metals. But, since there are insufficient quantities of dubnium produced, its chemical and physical properties are yet to be supported by scientific research.

It’s assumed that dubnium shares some of the chemical properties with the elements niobium and tantalum

How Was Dubnium Discovered?

Back when the Cold War between America and Russia was being waged on multiple fronts, the fields of science were the most significant battlefield for these two countries. The discovery of dubnium opened another cold-war battlefield in the realms of chemistry. 

The first 261Db isotope was produced in 1968 at the Russian Joint Institute for Nuclear Research at Dubna. Georgy N. Flerov led the team of researchers, and in their chemical experiment, they bombarded atoms of americium-243 with atoms of the neon-22 isotope. The result was an extremely radioactive isotope of element 105. 

A year later, in 1970, an American team of scientists working at the University of California at Berkeley, California, USA, succeeded in producing the same chemical element by bombarding californium-239 with nitrogen-15 atoms. Their scientific attempt produced the dubnium-261 isotope of the new element and confirmed the findings of the Russian research team. 

How Did Dubnium Get Its Name?

There’s a veil of controversy surrounding the story of how this element got its name. In the beginning, the name nielsbohrium (Ns) was proposed by the Russian team, who produced the first atoms of dubnium in 1968. They wanted to dedicate their discovery to the Danish nuclear physicist Niels Bohr.

But, after the American team of scientists from the Lawrence Berkeley Laboratory (LBL) managed to produce the same chemical element in 1970, they suggested the name hahnium (Ha), in honor of the Nobel Prize-winning chemist Otto Hahn.

In order to mediate the dispute between the two research teams who shared the credits for the discovery of dubnium, the IUPAC came up with the names unnilpentium and joliotium (after the French physicist Frédéric Joliot-Curie) for element 105 until the researchers reached a mutual decision on the element’s name. 

The IUPAC had made it clear that the element cannot be named after a person after they also rejected the name seaborgium for element 106. The International Union of Pure and Applied Chemistry officials also pointed out the fact that the University of Berkeley has already been recognized on several occasions (in the naming of the elements berkelium, californium, and americium).

Finally, in 1997 the name dubnium was given to the new chemical element after the Russian town Dubna, where the team of Soviet chemists discovered both rutherfordium and dubnium. 

Where Can You Find Dubnium?

Dubnium does not exist naturally in Earth’s crust because it’s a synthetic element with highly radioactive properties. There are only a few atoms produced of this substance.  

Dubnium in Everyday Life

Due to its hazardous radioactivity and the extremely small amounts in which it’s produced, dubnium is used only in scientific research and experimental chemistry in a highly controlled environment. Other than that, dubnium has no known practical uses. 

How Dangerous Is Dubnium?

If produced in large amounts, dubnium would be an extremely dangerous substance as a result of its high radioactivity. 

Environmental Effects of Dubnium

Due to the half-life of only 34 seconds and the extremely small amounts of this transuranium element, dubnium is not considered an environmental hazard. 

Isotopes of Dubnium

This chemical element counts 9 known isotopes, among which dubnium-268 is the longest-lived and only stable isotope of this chemical. With a half-life of 32 hours, 268Db decays through spontaneous fission. The mass numbers of dubnium isotopes range from 255 to 270, and they are all radioactive substances with extremely short half-lives. 



[n 1]

ZNIsotopic mass (Da)


[n 2][n 3]




[n 4]




Spin and



[n 5]

Excitation energy[n 6]
255Db[4]105150255.10707(45)#37(+51-14) msα (~50%)251Lr 
SF (~50%)(various)
256Db105151256.10789(26)#1.9(4) s


[1.6(+5−3) s]

α (~64%)252Lr 
SF (~0.02%)(various)
β+ (~36%)256Rf
257Db105152257.10758(22)#1.53(17) s


[1.50(+19−15) s]

α (>94%)253Lr(9/2+)
SF (<6%)(various)
β+ (1%)257Rf
257mDb140(100)# keV0.67(6) sα (>87%)253Lr(1/2−)
SF (<13%)(various)
β+ (1#%)257Rf
258Db105153258.10929(33)#4.5(4) sα (64%)254Lr 
β+ (36%)258Rf
SF (<1%)(various)
258mDb[n 7]60(100)# keV1.9(5) sβ+258Rf 
IT (rare)258Db
259Db105154259.10949(6)0.51(16) sα255Lr 
260Db105155260.1113(1)#1.52(13) sα (>90.4%)256Lr 
SF (<9.6%)(various)
β+ (<2.5%)260Rf
260mDb[n 7]200(150)# keV19 s   
261Db105156261.11192(12)#4.5(1.1) sSF (73%)(various) 
α (27%)257Lr
262Db105157262.11407(15)#35(5) sSF (~67%)(various) 
α (~30%)258Lr
β+ (3#%)262Rf
263Db105158263.11499(18)#29(9) s


[27(+10−7) s]

SF (~56%)(various) 
α (~37%)259Lr
β+ (~6.9%)[n 8]263Rf
266Db[n 9]105161266.12103(30)#80(70) minSF(various) 
267Db[n 10]105162267.12247(44)#4.6(3.7) hSF(various) 
268Db[n 11]105163268.12567(57)#30.8(5.0) hSF (>99%)(various) 
EC (<1%)268Rf
270Db[n 12]105165270.13136(64)#1.0 (+1.5−0.4) h[6]SF (~17%)(various) 
α (~83%)266Lr
EC (<1%)[7] 

Source: Wikipedia

5 Interesting Facts and Explanations

  1. IUPAC is the acronym of the International Union of Pure and Applied Chemistry. 
  2. The element dubnium has an assumed oxidation state of +5.
  3. The American team of chemists wanted to honor Otto Hahn, the father of nuclear chemistry, by naming the newly discovered element after him. 
  4. Dubnium is labeled as a super-heavy chemical element with an unstable electron configuration. 
  5. Nowadays, cold fusion reactions are used in scientific attempts to synthesize dubnium.