Fermium (symbol: Fm) is a synthetic chemical element and a member of the actinoid series. It is the heaviest element than can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities.
Discovery
Fermium was first discovered in the fallout from the 'Ivy Mike' nuclear test (1 November 1952), the first successful test of a hydrogen bomb. Initial examination of the debris from the explosion had shown the production of a new isotope of plutonium, 24494Pu: this could only have formed by the absorption of six neutrons by a uranium-238 nucleus followed by two β− decays. At the time, the absorption of neutrons by a heavy nucleus was thought to be a rare process, but the identification of 24494Pu raised the possibility that still more neutrons could have been absorbed by the uranium nuclei, leading to new elements.[4] Element 99 (einsteinium) was quickly discovered on filter papers which had been flown through the cloud from the explosion (the same sampling technique that had been used to discover 24494Pu), specifically the isotope 25499Es resulting from the capture of 16 neutrons by uranium-238 followed by seven β− decays.[4] The discovery of fermium (Z = 100) required more material, as the yield was expected to be at least an order of magnitude lower than that of element 99, and so contaminated coral from the Enewetak atoll (where the test had taken place) was shipped to the University of California Radiation Laboratory in Berkeley, California, for processing and analysis. About two months after the test, a new component was isolated emitting high-energy α-particles (7.1 MeV) with a half-life of about a day. With such a short half-life, it could only arise from the β− decay of an isotope of einsteinium, and so had to be an isotope of the new element 100: it was quickly identified as 255100Fm (t½ = 20.07 hours).[4]
Notes and references
Notes
- ↑ 1.0 1.1 1.2 Many of the properties of fermium are only known through estimation and/or extrapolation. The melting point and metallic radius were estimated on the basis of the enthalpy change of atomization and comparison with divalent lanthanoids; the electronegativity was estimated on the basis of periodic trends; the ionic radius was estimated from the behaviour of Fm3+ α-hydroxyisobutyrate (α-HIB) complexes on ion exchange columns, and agrees well with theoretical calculations. The electron configuration and thermodynamic properties are directly determined.
References
- ↑ 1.0 1.1 1.2 Haire, Richard G.; Gibson, John K. The enthalpy of sublimation and thermodynamic functions of fermium. J. Chem. Phys. 1989, 91 (11), 7085–96. DOI: 10.1063/1.457326.
- ↑ David, F.; Samhoun, K.; Guillaumont, R.; Edelstein, N. Thermodynamic properties of 5f elements. J. Inorg. Nucl. Chem. 1978, 40 (1), 69–74. DOI: 10.1016/0022-1902(78)80309-1.
- ↑ Brüchle, W.; Schädel, M.; Scherer, U. W.; Kratz, J. V.; Gregorich, K. E.; Lee, D.; Nurmia, M.; Chasteler, R. M., et al. The hydration enthalpies of Md3+ and Lr3+. Inorg. Chim. Acta 1988, 146 (2), 267–76. DOI: 10.1016/S0020-1693(00)80619-2.
- ↑ 4.0 4.1 4.2 Ghiorso, Albert Einsteinium and Fermium. Chem. Eng. News 2003, 81 (36), <http://pubs.acs.org/cen/80th/einsteiniumfermium.html>.
Further reading
- Hulet, E. K. Chemistry of the Heaviest Actinides: Fermium, Mendelevium, Nobelium, and Lawrencium. In Lanthanide and Actinide Chemistry and Spectroscopy; Edelstein, Norman M., Ed.; American Chemical Society: Washington, D.C.; Chapter 12, pp 239–63. ACS Symposium Series, Vol. 131. ISBN 9780841205680. DOI: 10.1021/bk-1980-0131.ch012.
- Silva, Robert J. Fermium, Mendelevium, Nobelium, and Lawrencium. In The Chemistry of the Actinide and Transactinide Elements, 3rd ed.; Morss, Lester R.; Edelstein, Norman M.; Fuger, Jean, Eds.; Springer: Dordrecht, 2006; Vol. 3, Chapter 13, pp 1621–51. doi:10.1007/1-4020-3598-5_13, <http://radchem.nevada.edu/classes/rdch710/files/Fm%20to%20Lr.pdf>
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