Dubnium (105)

Dubnium is a synthetic element that is not present in the environment at all. It has no uses.

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 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

Historical information

Dubnium apparently was synthesized by Russian and American workers independently by bombardment technologies. Its actual isolation as the free element has not been accomplished. In 1967, Flerov reported element 105 after experiments at the Joint Research Institute in Russia involving reactions between²⁴³Am ions with ²²Ne ions. In 1970, Ghiorso and others announced their synthesis of dubnium at Berkeley (California) in the USA. This method involved the collision of²⁴⁹Cf ions with ¹⁵N ions.

Dubnium was reportedly first discovered in 1968 at the Joint Institute for Nuclear Research at Dubna (then in the Soviet Union). Researchers there bombarded an americium-243 target with neon-22 ions. They reported a 9.40 MeV and a 9.70 MeV alpha-activity and assigned the decays to the isotope ²⁶⁰Db or ²⁶¹Db:

243
95Am + 22
10Ne → 265−x
105Db + x n

Two years later, the Dubna team separated their reaction products by thermal gradient chromatography after conversion to chlorides by interaction with NbCl₅. The team identified a 2.2 second spontaneous fission activity contained within a volatile chloride portraying eka-tantalum properties, likely dubnium-261 pentachloride, ²⁶¹DbCl₅.

In the same year, a team led by Albert Ghiorso working at the University of California, Berkeley conclusively synthesized the element by bombarding a californium-249 target with nitrogen-15 ions. The team published a convincing synthesis of ²⁶⁰Db in the reaction between californium-249 target and nitrogen-15 ions and measured the alpha decay of ²⁶⁰Db with a half-life of 1.6 seconds and a decay energy of 9.10 MeV, correlated with the daughter decay of lawrencium-256:

249
98Cf + 15
7N → 260
105Db + 4 n

These results by the Berkeley scientists did not confirm the Soviet findings regarding the 9.40 MeV or 9.70 MeV alpha-decay of dubnium-260, leaving only dubnium-261 as possible produced isotope. In 1971, the Dubna team repeated their reaction using an improved set-up; they were able to confirm the decay data for ²⁶⁰Db using the reaction:

243
95Am + 22
10Ne → 260
105Db + 5 n

In 1976, the Dubna team continued their study of the reaction using thermal gradient chromatography. They were able to identify the products as dubnium-260 pentabromide ( ²⁶⁰DbBr₅).
In 1992 the IUPAC/IUPAP Transfermium Working Group assessed the claims of the two groups and concluded that confidence in the discovery grew from results from both laboratories and the claim of discovery should be shared.

Choosing a name…say it isn’t so!

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. Consequently hahnium was the name that most American and Western European scientists used and appears in many papers published at the time, and nielsbohrium was used in the Soviet Union and Eastern Bloccountries.

An element naming controversy erupted between the two groups. The International Union of Pure and Applied Chemistry (IUPAC) thus adopted unnilpentium(Unp) as a temporary, systematic element name. Attempting to resolve the issue, in 1994, the IUPAC proposed the name joliotium (Jl), after the French physicistFrédéric Joliot-Curie, which was originally proposed by Soviet team for element 102, later named nobelium. The two principal claimants still disagreed about the names of elements 104-106. However, in 1997 they resolved the dispute and adopted the current name, dubnium (Db), after the Russian town of Dubna, the location of the Joint Institute for Nuclear Research. It was argued by IUPAC that the Berkeley laboratory had already been recognized several times in the naming of elements (i.e., berkelium, californium, americium) and that the acceptance of the names rutherfordium and seaborgium for elements 104 and 106 should be offset by recognizing the Russian team's contributions to the discovery of elements 104, 105 and 106.

Dubnium: physical properties

• Melting point: no data K
• Boiling point: no data K
• Density of solid: 29.3 g cm-1 or 21600 (predicted) kg m^-3

Dubnium: orbital properties

• Ground state electron configuration:  [Rn].5f¹⁴.6d³.7s² (a guess based upon that of tantalum)
• Shell structure:  2.8.18.32.32.11.2
• Term symbol:   ⁴F_3/2 (a guess based upon guessed electronic structure)

Isolation

Only very small amounts of of element 105, dubnium, have ever been made. were made through nuclear reactions involving fusion of an isotope of californium, ²⁴⁹Cf, with one of nitrogen The first samples, ¹⁴N. A second route to the same isotope via berkelium is also known

¹⁵N + ²⁴⁹Cf → ²⁶¹₁₀₅Db + 4 ¹n

¹⁶N + ²⁴⁹Bk → ²⁶¹₁₀₅Db + 4 ¹n

Isolation of an observable quantity of dubnium has never been achieved.