Description
تفصیل
Dubnium (doob-nee- əm)is a chemical element with the symbol "Db" and atomic number 105, named after the town of Dubna in Russia, where it was first produced. It is a synthetic element (an element that can be created in a laboratory but is not found in nature) and radioactive; the most stable known isotope, dubnium-268, has a half-life of approximately 28 hours.
In the periodic table of the elements, it is a d-block element and in the transactinide elements. It is a member of the period 7 and a group 5 element. Chemistry experiments have confirmed that dubnium behaves as the heavier homologue to tantalum in group 5. The chemical properties of dubnium are characterized only partly. They are similar with those of other group 5 elements.
In the 1960s, microscopic amounts of dubnium were produced in laboratories in the former Soviet Union and in California. The priority of the discovery and therefore the naming of the element was disputed between Soviet and American scientists, and it was not until 1997 that International Union of Pure and Applied Chemistry (IUPAC) established Soviet team priority and a compromise name of dubnium as the official name for the element.
Dubnium was first reported by Russian scientists in 1968 at the Joint Institute for Nuclear Research in Dubna, Soviet Union (now in Russia). Researchers there bombarded a 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 isotopes 260Db or 261Db.
243
95Am + 22
10Ne → 265−x
105Db + x n
In 1970 Soviet team expanded their work by the application of thermal gradient chromatography and detection by spontaneous fission. They observed a 2.2 second spontaneous fission activity in a fraction portraying niobium-like characteristics and assigned the activity to dubnium-261 pentachloride, 261DbCl5.
In 1976, the Russian team continued their study of the reaction using thermal gradient chromatography and were able to identify the product dubnium-260 pentabromide, 260DbBr5.
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 Bloc countries.
References:
^ Münzenberg, G.; Gupta, M. (2011). Production and Identification of Transactinide Elements. pp. 877. doi:10.1007/978-1-4419- 0720-2_19.
^ http://newscenter.lbl.gov/news- releases/2010/10/26/six-new-isotopes/
^ Oganessian, Yu. Ts.; Abdullin, F. Sh.; Bailey, P. D.; Benker, D. E.; Bennett, M. E.; Dmitriev, S. N.; Ezold, J. G.; Hamilton, J. H. et al. (2010). "Synthesis of a New Element with Atomic Number Z=117". Physical Review Letters 104. doi:10.1103/PhysRevLett.104.142502. PMID 20481935.
^ Merriam-Webster's Collegiate Dictionary -Eleventh Edition, Merriam-Webster, Inc, 2003
^ Physical experiments determined a half- life of ~16 h whilst chemical experiments provided a value of ~32 h. The half-life is often taken as ~28 h due to the higher number of atoms detected by chemical means
^ Barber, R. C.; Greenwood, N. N.; Hrynkiewicz, A. Z.; Jeannin, Y. P.; Lefort, M.; Sakai, M.; Ulehla, I.; Wapstra, A. P. et al. (1993). "Discovery of the transfermium elements. Part II: Introduction to discovery profiles. Part III: Discovery profiles of the transfermium elements (Note: for Part I see Pure Appl. Chem., Vol. 63, No. 6, pp. 879–886, 1991)". Pure and Applied Chemistry 65 (8): 1757. doi:10.1351/pac199365081757.
^ "Names and symbols of transfermium elements (IUPAC Recommendations 1994)". Pure and Applied Chemistry 66 (12): 2419. 1994. doi:10.1351/pac199466122419.
^ "Names and symbols of transfermium elements (IUPAC Recommendations 1997)". Pure and Applied Chemistry 69 (12): 2471. 1997. doi:10.1351/pac199769122471.
^ Munzenberg; Hofmann, S.; Heßberger, F. P.; Reisdorf, W.; Schmidt, K. H.; Schneider, J. H. R.; Armbruster, P.; Sahm, C. C. et al. (1981). "Identification of element 107 by α correlation chains". Z. Phys. A. 300: 1. Bibcode 1981ZPhyA.300..107M. doi:10.1007/BF01412623.
^ Hessberger; Münzenberg, G.; Hofmann, S.; Agarwal, Y. K.; Poppensieker, K.; Reisdorf, W.; Schmidt, K. -H.; Schneider, J. R. H. et al. (1985). "The new isotopes 258105,257105,254Lr and 253Lr". Z. Phys A. 322 (4): 4. Bibcode 1985ZPhyA.322..557H. doi:10.1007/BF01415134.
^ F. P. Hessberger; Hofmann, S.; Ackermann, D.; Ninov, V.; Leino, M.; Münzenberg, G.; Saro, S.; Lavrentev, A. et al. (2001). "Decay properties of neutron-deficient isotopes 256,257Db, 255Rf, 252,253Lr". Eur. Phys. J. A 12: 57–67. Bibcode 2001EPJA...12...57H. doi:10.1007/s100500170039.
^ F. P. Hessberger; Antalic, S.; Streicher, B.; Hofmann, S.; Ackermann, D.; Kindler, B.; Kojouharov, I.; Kuusiniemi, P. et al. (2005). "Energy systematics of low-lying Nilsson levels in odd-mass einsteinium isotopes". Eur. Phys. J. A 26 (2): 2. Bibcode 2005EPJA...26..233H. doi:10.1140/epja/i2005- 10171-6.
^ Gates (2005). "Measurement of the 208Pb (51V, xn)259-xDb Excitation Function". LBNL Annual Report.
^ "238U studies". Retrieved 2009-05-05.
^ A. N. Andreyev; Bogdanov, D. D.; Chepigin, V. I.; Kabachenko, A. P.; Malyshev, O. N.; Oganessian, Yu. Ts.; Sagajdak, R. N.; Ter-Akopian, G. M. et al. (1992). "Investigation of the fusion reaction 27Al + 236U → 263105 at excitation energies of 57 MeV and 65 MeV". Z. Phys. A. 344 (2): 2. Bibcode 1992ZPhyA.344..225A. doi:10.1007/BF01291709.
