Dubnium (Db)

Isotopes of Dubnium 

Isotope Mass Half-life Mode of decay Nuclear spin Nuclear magnetic moment
Db-255 255.1074 1.60 seconds α to Lr-251;
No data available  No data available 
Db-256 256.1081 2.60 seconds α to Lr-252; SF;
EC to Rf-256
No data available  No data available 
Db-257 257.1079 1.50 seconds α to Lr-253; SF;
EC to Rf-257
No data available  No data available 
Db-258 258.1093 4.20 seconds α to Lr-254; SF;
EC to Rf-258
No data available  No data available 
Db-259 259.1097 1.20 seconds α to Lr-255 No data available  No data available 
Db-260 260.1114 1.50 seconds α to Lr-256; SF;
EC to Rf-260
No data available  No data available 
Db-261 261.1121 1.80 seconds α to Lr-257; SF No data available  No data available 
Db-262 262.11376 34 seconds α to Lr-258; SF;
EC to Rf-262
No data available  No data available 
Db-263 263.1153 30 seconds α to Lr-259; SF No data available  No data available 


Dubnium is a synthetic element (an element that can be created in a laboratory but is not found in nature). It apparently was synthesized by Russian and American workers independently by bombardment technologies in the 1960s. Its actual isolation as the free element has not been accomplished. The priority of the discovery, and therefore the naming of the element, was disputed among Soviet and American scientists. The Soviet, later Russian, team proposed the name nielsbohrium (Ns) in honor of the Danish nuclear physicist Niels Bohr. The American team proposed that the new element should be named hahnium (Ha), in honor of the late German chemist Otto Hahn. In 1997 the dispute was resolved, and the current name "dubnium" (Db) adopted, after the Russian town of Dubna, the location of the Joint Institute for Nuclear Research, an institute prominently involved in the search for heavy elements.

The chemistry of dubnium has been studied for several years using gas thermochromatography, studying the relative adsorption characteristics of isotopes of niobium, tantalum and dubnium. Results indicate the formation of typical group 5 halides and oxyhalides. 

Properties of Dubnium

Name Dubnium
Symbol Db
Atomic number 105
Atomic weight [268]
Standard state Presumably a solid at 298 °K
CAS Registry ID 53850-35-4
Group in periodic table 5
Group name None
Period in periodic table 7
Block in periodic table d-block
Color Unknown, but probably metallic and silvery white or grey in appearance
Classification Metallic
Melting point No data available
Boiling point No data available
Density of solid 21.6 g/cm3 (predicted)
Electron configuration [Rn]5f146d37s2


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