Dubnium (Db)
Dubnium (Db) is a radioactive transition metal with the atomic number 105, positioned in the periodic table's seventh row, specifically in the actinide series. As a synthetic element, dubnium does not occur naturally and was first produced in 1967 by Soviet scientists at the Joint Institute for Nuclear Research in Dubna, Russia, and later by U.S. scientists at the Lawrence Livermore National Laboratory in 1970. It is notably the heaviest metal in Group 5 and is characterized by a predicted metallic appearance and a density of approximately 29.3 grams per cubic centimeter. Dubnium has twelve known isotopes, all of which are unstable, with dubnium-268 being the most stable, having a half-life of thirty-two hours.
Chemically, dubnium displays oxidation states of +3, +4, and +5, and its electron configuration is [Rn]5f 14 6d 3 7s 2. Despite its theoretical properties, much remains uncertain about its physical and chemical characteristics due to the limited quantities produced, which are primarily used for research. Extreme caution is necessary when handling dubnium, as it is radioactive. Overall, dubnium represents a fascinating subject of study within nuclear chemistry and physics, although its practical applications are currently limited to research contexts.
Subject Terms
Dubnium (Db)
- Element Symbol: Db
- Atomic Number: 105
- Atomic Mass: 262
- Group # in Periodic Table: 5
- Group Name: Transition metals
- Period in Periodic Table: 7
- Block of Periodic Table: d-block
- Discovered by: Joint Institute for Nuclear Research, Dubna, Soviet Union (1967)
Dubnium is a radioactive transition metal whose chemical symbol is Db. It is one of the transactinide metallic elements. Transactinide elements are those whose atomic numbers are larger than that of actinides. This name reflects the position of these elements in the periodic table. The first element in the series is rutherfordium; the last element is ununoctium. The atomic numbers in that group range from 104 to 118. Dubnium has an atomic number of 105. In the periodic table, dubnium is located in row 7, the actinide-series row. This position places the element below tantalum and between rutherfordium and seaborgium (named after physicist Ernest Rutherford and chemist Glenn T. Seaborg, respectively). Because it falls in this row, its period number is 7. It is also a d-block element, which means it belongs to the group of elements that are called the transition elements. These elements are metals that form chemical bonds in two or more ways. It belongs to the 6d series. It is the heaviest metal in Group 5. Dubnium does not occur naturally in the environment. It is a synthetic element that was produced by scientists at two facilities: at the Joint Institute for Nuclear Research (JINR) in Dubna (close to Moscow), Russia, in 1967, and also at the Lawrence Radiation Laboratory, now known as the Lawrence Livermore National Laboratory, in Berkeley, California, in 1970. The Soviet scientists bombarded atoms of americium-243 with ions of neon-22. This procedure resulted in the production of atoms of dubnium-260 and five free neutrons as well as atoms of dubnium-261 and four free neutrons. The U.S. scientists bombarded atoms of californium-249 with ions of nitrogen-15. This procedure produced atoms of dubnium-260 and four free neutrons. The two teams of scientists both claimed credit for discovering the element, and so each group sought its naming rights. Soviet scientists suggested that the element be named after Danish nuclear physicist Niels Bohr, whereas the U.S. scientists recommended the name of German chemist Otto Hahn, father of nuclear chemistry. Dubnium was accepted as the official name in 1997 almost twenty years after the element’s discovery.
Physical Properties
Since only small quantities of dubnium have been produced, not much is known about the element. Its color is unknown, but the element is predicted to be metallic, with a silvery-white or grey luster. It has an atomic mass of 268. The standard state of an element is defined as its state at 298 K. It is theorized that dubnium is a solid at this temperature. The density of dubnium is predicted to be 29.3 grams per cubic centimeter.
Several other properties of dubnium still remain to be studied—for example, its melting point, boiling point, specific gravity, specific heat, thermal conductivity, and electrical conductivity, among other properties.
Chemical Properties
Dubnium is predicted to have a body-centered cubic crystal structure. The most common oxidation states of dubnium are +5; dubnium may also form +4, and +3 oxidation states. Each oxidation state has its characteristic spectrum. Dubnium’s electron configuration is[Rn]5f146d37s2. The chemical properties of dubnium are generally studied using gas thermochromatography. However, much remains to be discovered regarding the element’s chemical properties.
Its first ionization energy is predicted to be 664.8 kilojoules per mole. Dubnium has twelve known isotopes, none of which are stable. The element can decay through spontaneous fission. The mass numbers of the isotopes range from 256 to 270. The most stable isotope is dubnium-268, which has a half-life of thirty-two hours. All of the other isotopes have short half-lives. Dubnium is difficult to extract; scientists have tried to extract the element using hot fusion and cold fusion methods. Dubnium-268 is produced from americium-243 or californium-249, and it decays into lawrencium-258 and finally into mendelevium-254. Isotopes of dubnium have been identified in the decay of heavier elements. It is predicted that isotopes of dubnium have a longer half-life.
Applications
Because dubnium is not a naturally occurring element, it has to be synthesized. Only small quantities of this element have been created. As a result, the element is currently of interest for research purposes only. Since it is a radioactive element, extreme care should be taken to ensure that it is handled only by experts who are taking the necessary precautions.
Bibliography
"Dubnium." Periodic Table. Royal Society of Chemistry, n.d. Web. 20 Feb. 2016. <www.rsc.org/periodic-table/element/105/dubnium>.
"Dubnium." Periodic Table. Wolfram Research, n.d. Web. 20 Feb. 2016.
<http://www.periodictable.com/Elements/105/index.html>.
Editors of Encyclopaedia Britannica. "Dubnium (Db)." Encyclopaedia Britannica. Encyclopaedia Britannica, Inc., n.d. Web. 20 Feb. 2016. <http://www.britannica.com/science/dubnium>.
Hall, Linley E. The Transactinides: Rutherfordium, Dubnium, Seaborgium, Bohrium, Hassium, Meitnerium, Darmstadtium, Roentgenium (Understanding the Elements of the Periodic Table). New York: Rosen Publishing, 2010. Print.