Overview

Dubnium is a synthetic chemical element with the symbol Db and an assigned atomic number of 105. It is not found in the Earth’s crust and must be created artificially in laboratories using nuclear reactions. All known atoms of dubnium are radioactive and short-lived, so the element is studied chiefly for basic research into the behavior of very heavy nuclei and the properties of the periodic table at extreme proton numbers.

Characteristics

As a member of the group commonly associated with the transition metals, dubnium is expected to show properties similar to other group 5 elements in the periodic table. Experimental chemical studies have been carried out on trace amounts of dubnium and indicate it behaves in ways comparable to niobium and tantalum under certain conditions. Because only tiny quantities are available, most data are inferred from periodic trends and from short chemical experiments rather than bulk physical measurements.

Isotopes and stability

All dubnium isotopes are radioactive. Laboratory synthesis has produced several nuclides with differing neutron counts; the identity and decay modes of these isotopes are established by nuclear detectors. The known isotopes have half-lives that are brief—typically seconds to hours—and the most long-lived species has a half-life measured on the order of tens of hours. For details of specific isotopes and their measured decay properties see summaries of synthetic transuranium nuclides such as individual isotope entries.

History and discovery

Atoms of element 105 were first reported in experiments performed by research teams that used heavy-ion accelerators and target materials. Early work involved bombardment of actinide targets with light nuclei; for example, researchers used californium targets struck by nitrogen or similar projectiles to produce DB atoms in detectable quantities. The element’s discovery involved multiple laboratories and led to discussion over credit and naming; the accepted name honors the Russian research center at Dubna where important contributions were made.

Production and laboratory methods

Dubnium is produced in particle accelerators by fusing lighter nuclei to make a heavier nucleus, a process typical for transuranium and transactinide elements. Production rates are extremely low: only a few atoms may be generated in a single experiment. After production, rapid separation and detection techniques identify decay chains and enable short chemical experiments. Target and projectile combinations used historically include californium and nitrogen isotopes among others.

Uses and significance

There are no practical or commercial applications for dubnium outside fundamental research because of its scarcity and radioactivity. Its importance lies in expanding knowledge of nuclear stability, testing predictions of relativistic effects in heavy-element chemistry, and refining the organization of the periodic table at very large atomic numbers. For concise technical overviews and reference tables consult specialized nuclear data compilations and research reviews (decay data, element summaries, general references, isotope lists, synthesis methods, classification).

  • Symbol: Db
  • Atomic number: 105 (Z = 105)
  • Occurrence: synthetic only
  • Primary use: scientific research