Difference between revisions of "Mendelevium"
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==Preparation== | ==Preparation== | ||
| − | Mendelevium was first prepared at the [[University of California Radiation Laboratory]] in Berkeley, California, in 1955 by the bombardment of {{Nuclide|A=253|Z=99}} targets (roughly 10<sup>9</sup> atoms) with 41 MeV [[α-particle]]s: just two atoms of the new element, later confirmed to be the ''A'' = 256 isotope, were produced per three-hour bombardment session, and only seventeen atoms in total were detected.<ref name="55Gh99">{{citation | last1 = Ghiorso | first1 = A. | authorlink1 = Albert Ghiorso | last2 = Harvey | first2 = B. G. | last3 = Choppin | first3 = G. R. | last4 = Thompson | first4 = S. G. | authorlink4 = Stanley G. Thompson | last5 = Seaborg | first5 = G. T. | authorlink5 = Glenn T. Seaborg| title = New Element Mendelevium, Atomic Number 101 |year=1955 | journal = Phys. Rev. | volume = 98 | issue = 5 | pages = 1518–19 | doi=10.1103/PhysRev.98.1518}}.</ref> The new element was identified by its elution time in [[ion-exchange chromatography]]: a [[spontaneous fission]] activity was observed both in the fermium fraction and in a fraction that eluted before the fermium, and this was taken to be a fermium daughter isotope produced by [[electron-capture decay]] of an isotope of element 101.<ref name="55Gh99"/> A larger-scale preparation in 1958 demostrated a parent–daughter relationship between <sup>255</sup>101 and the previously-described <sup>255</sup>Fm.<ref name="58Ph40">{{citation | first1 = L. | last1 = Phillips | first2 = R. | last2 = Gatti | first3 = A. | last3 = Chesne | first4 = L. | last4 = Muga | first5 = S. | last5 = Thompson | title = Discovery of a new Mendelevium Isotope | journal = Phys. Rev. Lett. | year = 1958 | volume = 1 | issue = 6 | pages = 215–21 | doi = 10.1103/PhysRevLett.1.215}}.</ref> | + | Mendelevium was first prepared at the [[University of California Radiation Laboratory]] in Berkeley, California, in 1955 by the bombardment of {{Nuclide|A=253|Z=99}} targets (roughly 10<sup>9</sup> atoms) with 41 MeV [[α-particle]]s: just two atoms of the new element, later confirmed to be the ''A'' = 256 isotope, were produced per three-hour bombardment session, and only seventeen atoms in total were detected.<ref name="55Gh99">{{citation | last1 = Ghiorso | first1 = A. | authorlink1 = Albert Ghiorso | last2 = Harvey | first2 = B. G. | last3 = Choppin | first3 = G. R. | last4 = Thompson | first4 = S. G. | authorlink4 = Stanley G. Thompson | last5 = Seaborg | first5 = G. T. | authorlink5 = Glenn T. Seaborg | title = New Element Mendelevium, Atomic Number 101 |year=1955 | journal = Phys. Rev. | volume = 98 | issue = 5 | pages = 1518–19 | doi=10.1103/PhysRev.98.1518}}.</ref> The new element was identified by its elution time in [[ion-exchange chromatography]]: a [[spontaneous fission]] activity was observed both in the fermium fraction and in a fraction that eluted before the fermium, and this was taken to be a fermium daughter isotope produced by [[electron-capture decay]] of an isotope of element 101.<ref name="55Gh99"/> A larger-scale preparation in 1958 demostrated a parent–daughter relationship between <sup>255</sup>101 and the previously-described <sup>255</sup>Fm.<ref name="58Ph40">{{citation | first1 = L. | last1 = Phillips | first2 = R. | last2 = Gatti | first3 = A. | last3 = Chesne | first4 = L. | last4 = Muga | first5 = S. | last5 = Thompson | authorlink5 = Stanley G. Thompson | title = Discovery of a new Mendelevium Isotope | journal = Phys. Rev. Lett. | year = 1958 | volume = 1 | issue = 6 | pages = 215–21 | doi = 10.1103/PhysRevLett.1.215}}.</ref> |
| − | The preparation of mendelevium still follows the same principles | + | The preparation of mendelevium still follows the same principles, although production rates of about a million atoms per hour can now be obtained.<ref>{{citation | last1 = Hulet | first1 = E. K. | last2 = Lougheed | first2 = R. W. | last3 = Brady | first3 = J. D. | last4 = Stone | first4 = R. E. | last5 = Coops | first5 = M. S. | title = Mendelevium: Divalency and Other Chemical Properties | journal = Science | year = 1967 | volume = 158 | pages = 486–88 | doi = 10.1126/science.158.3800.486}}.</ref> The mendelevium atoms are collected on a thin metal film placed behind the [[einsteinium]] target (either <sup>253</sup>Es or the longer-lived <sup>254</sup>Es), or are carried in a stream of inert gas to a separate collection area. The collector foil is then dissolved in acid and the mendelevium is coprecipitated with [[lanthanum fluoride]]. The mendelevium is then separated from the lanthanum carrier and any lanthanoid fission products by ion-exchange chromatography using 10% aqueous [[ethanol]] saturated with [[hydrogen chloride]] as the eluant.<ref>{{citation | last1 = Thompson | first1 = S. G. | authorlink1 = Stanley G. Thompson | last2 = Harvey | first2 = B. G. | last3 = Choppin | first3 = G. R. | last4 = Seaborg | first4 = G. T. | authorlink4 = Glenn T. Seaborg | title = Chemical Properties of Elements 99 and 100 | journal = J. Am. Chem. Soc. | year = 1954 | volume = 76 | issue = 24 | pages = 6229–36 | doi = 10.1021/ja01653a004}}.</ref> Final purification is acheived again by ion-exchange chromatography, this time using aqueous [[ammonium α-hydroxyisobutyrate]] as the eluant.<ref>{{citation | last1 = Choppin | first1 = G. R. | last2 = Harvey | first2 = B. G. | last3 = Thompson | first3 = S. G. | authorlink3 = Stanley G. Thompson | title = A new eluant for the separation of the actinide elements | journal = J. Inorg. Nucl. Chem. | year = 1956 | volume = 2 | issue = 1 | pages = 66–68 | doi = 10.1016/0022-1902(56)80105-X}}.</ref> |
==Notes and references== | ==Notes and references== | ||
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Mendelevium (symbol: Md) is a synthetic chemical element and a member of the actinoid series. It cannot be formed by neutron bombardment in a nuclear reactor, but must instead be produced in particle accelerators. Mendelevium cannot be produced in macroscopic quantities.
It was first prepared in 1955, and named after Dmitri Mendeleev. Its chemistry is typical of the late actinoids, with both the +3 and +2 oxidation states stable in aqueous solution.
Contents
Preparation
Mendelevium was first prepared at the University of California Radiation Laboratory in Berkeley, California, in 1955 by the bombardment of 25399Es targets (roughly 109 atoms) with 41 MeV α-particles: just two atoms of the new element, later confirmed to be the A = 256 isotope, were produced per three-hour bombardment session, and only seventeen atoms in total were detected.[5] The new element was identified by its elution time in ion-exchange chromatography: a spontaneous fission activity was observed both in the fermium fraction and in a fraction that eluted before the fermium, and this was taken to be a fermium daughter isotope produced by electron-capture decay of an isotope of element 101.[5] A larger-scale preparation in 1958 demostrated a parent–daughter relationship between 255101 and the previously-described 255Fm.[6]
The preparation of mendelevium still follows the same principles, although production rates of about a million atoms per hour can now be obtained.[7] The mendelevium atoms are collected on a thin metal film placed behind the einsteinium target (either 253Es or the longer-lived 254Es), or are carried in a stream of inert gas to a separate collection area. The collector foil is then dissolved in acid and the mendelevium is coprecipitated with lanthanum fluoride. The mendelevium is then separated from the lanthanum carrier and any lanthanoid fission products by ion-exchange chromatography using 10% aqueous ethanol saturated with hydrogen chloride as the eluant.[8] Final purification is acheived again by ion-exchange chromatography, this time using aqueous ammonium α-hydroxyisobutyrate as the eluant.[9]
Notes and references
Notes
References
- ↑ Pauling, Linus The Nature of the Chemical Bond, 3rd ed.; Ithaca, NY, 1960; pp 88–95. ISBN 0-8014-0333-2.
- ↑ 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.
- ↑ Haire, R. G.; Gibson, J. K. Selected systematic properties and some recent investigations of actinide metals and alloys. J. Radioanal. Nucl. Chem. 1990, 143 (1), 35–51. DOI: 10.1007/BF02117545.
- ↑ 5.0 5.1 Ghiorso, A.; Harvey, B. G.; Choppin, G. R.; Thompson, S. G.; Seaborg, G. T. New Element Mendelevium, Atomic Number 101. Phys. Rev. 1955, 98 (5), 1518–19. DOI: 10.1103/PhysRev.98.1518.
- ↑ Phillips, L.; Gatti, R.; Chesne, A.; Muga, L.; Thompson, S. Discovery of a new Mendelevium Isotope. Phys. Rev. Lett. 1958, 1 (6), 215–21. DOI: 10.1103/PhysRevLett.1.215.
- ↑ Hulet, E. K.; Lougheed, R. W.; Brady, J. D.; Stone, R. E.; Coops, M. S. Mendelevium: Divalency and Other Chemical Properties. Science 1967, 158, 486–88. DOI: 10.1126/science.158.3800.486.
- ↑ Thompson, S. G.; Harvey, B. G.; Choppin, G. R.; Seaborg, G. T. Chemical Properties of Elements 99 and 100. J. Am. Chem. Soc. 1954, 76 (24), 6229–36. DOI: 10.1021/ja01653a004.
- ↑ Choppin, G. R.; Harvey, B. G.; Thompson, S. G. A new eluant for the separation of the actinide elements. J. Inorg. Nucl. Chem. 1956, 2 (1), 66–68. DOI: 10.1016/0022-1902(56)80105-X.
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., 1980; Chapter 12, pp 239–63. ACS Symposium Series, Vol. 131. ISBN 9780841205680. DOI: 10.1021/bk-1980-0131.ch012.
- Seaborg, Glenn T. The transcalifornium elements. J. Chem. Educ. 1959, 36 (1), 38–44. DOI: 10.1021/ed036p38.
External links
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See also the corresponding article on Wikipedia. |
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