Protactinium (symbol: Pa) is a chemical element, a member of the actinoid series. Although all isotopes of protactinium are unstable, protactinium-231 (t½ = 3.276(11) × 104 a)[7] is formed as a decay product of uranium-235 (t½ = 704(1) × 106 a) and so small amounts of protactinium are present in all samples of natural uranium.
The existence of an element between thorium and uranium was predicted in 1872 by Mendeleev, who named the putative element eka-tantalum. The chemistry of protactinium does resemble that of niobium and tantalum, with a preponderence of the +5 oxidation state, and periodic tables from before the Second World War often placed protactinium as a transition metal.
Notes and references
Notes
- ↑ The configuration [Rn] 5f1 6d2 7s2 is given as a possible alternative in some textbooks.
References
- ↑ 1.0 1.1 Myasoedov, Boris F.; Kirby, H. W.; Tananaev, Ivan G. Protactinium. In The Chemistry of the Actinide and Transactinide Elements, 3rd ed.; Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean, Eds.; Springer: Dordrecht, the Netherlands, 2006; Vol. 1, Chapter 4, pp 161–252. doi:10.1007/1-4020-3598-5_4, <http://radchem.nevada.edu/classes/rdch710/files/protactinium.pdf>.
- ↑ 2.0 2.1 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1450–86. ISBN 0-08-022057-6.
- ↑ Pauling, Linus The Nature of the Chemical Bond, 3rd ed.; Ithaca, NY, 1960; pp 88–95. ISBN 0-8014-0333-2.
- ↑ Sugar, Jack Ionization energies of the neutral actinides. J. Chem. Phys. 1973, 59, 788–91. DOI: 10.1063/1.1680091. Sugar, Jack Revised ionization energies of the neutral actinides. J. Chem. Phys. 1974, 60, 4103. DOI: 10.1063/1.1680874.
- ↑ Cordero, Beatriz; Gómez, Verónica; Platero-Prats, Ana E.; Revés, Marc; Echeverría, Jorge; Cremades, Eduard; Barragán, Flavia; Alvarez, Santiago Covalent radii revisited. Dalton Trans. 2008 (5), 2832–38. DOI: 10.1039/b801115j.
- ↑ Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halids and chalcogenides. Acta Crystallogr. A 1976, 32 (5), 751–67. DOI: 10.1107/S0567739476001551.
- ↑ Audi, G.; Bersillon, O.; Blachot, J.; Wapstra, A. H. The NUBASE evaluation of nuclear and decay properties. Nucl. Phys. A 2003, 729, 3–128. doi:10.1016/j.nuclphysa.2003.11.001, <http://amdc.in2p3.fr/nubase/Nubase2003.pdf>.
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