Americium

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plutoniumamericiumcurium
Eu

Am

Atomic properties
Atomic number 95
Electron configuration [Rn] 5f7 7s2
Physical properties[1][2][3]
Melting point 876(5) °C (1149(5) K)
Boiling point 2067 °C (2340 K)
Density 13.671 g cm−3
Electric resistivity 68 × 10−6 Ω cm
Chemical properties[4]
Electronegativity 1.3 (Pauling)
Ionization energies[5][6]
1st 5.9738(2) eV,
576.38(2) kJ mol−1
2nd 12.5 eV
1206 kJ mol−1
3rd 18.8 eV
1814 kJ mol−1
Atomic radii[2][7][8]
Covalent radius 180 pm
Metallic radius 173 pm
Ionic radius 85 pm (Am4+, Oh)
97.5 pm (Am3+, Oh)
121 pm (Am2+, Oh)
Thermodynamic properties[1][9]
Standard entropy 55 J K−1 mol−1
Enthalpy change of fusion 14.4 kJ mol−1
Enthalpy change of vaporization 230.2 kJ mol−1
Molar heat capacity (Cp) 25.5 J K−1 mol−1
Miscellaneous
CAS number 7440-35-9
EC number 231-144-4
Where appropriate, and unless otherwise stated, data are given for 100 kPa (1 bar) and 298.15 K (25 °C).

Americium (symbol: Am) is a synthetic chemical element, a member of the actinoid series. It is produced in commercial nuclear reactors, although it is not currently extracted during normal fuel reprocessing: nevertheless, kilogram quantities of 241Am (t½ = 432.2(7) a) and 243Am (t½ = 7.37(4) × 103 a) are available from the reprocessing of specialized fuel batches.[1] It has a number of small-scale commercial uses, particularly in domestic smoke alarms.

Americium was first prepared in 1944 in the University of Chicago Metallurgical Laboratory.[10] It was named after the continent of America, by analogy with europium, its lanthanoid homologue, named after the continent of Europe.

Notes and references

Notes

References

  1. 1.0 1.1 1.2 Runde, Wolfgang H.; Schulz, Wallace W. Americium. 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. 3, Chapter 8, pp 1265–1395. doi:10.1007/1-4020-3598-5_8, <http://radchem.nevada.edu/classes/rdch710/files/americium.pdf>.
  2. 2.0 2.1 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1450–86. ISBN 0-08-022057-6.
  3. Electrical resistivities. In Kaye & Laby Tables of Physical & Chemical Constants, 16th ed., 1995; Chapter 2.6.1, <http://www.kayelaby.npl.co.uk/general_physics/2_6/2_6_1.html>. (accessed 4 April 2011).
  4. Pauling, Linus The Nature of the Chemical Bond, 3rd ed.; Ithaca, NY, 1960. ISBN 0-8014-0333-2.
  5. Deissenberger, Rüdiger; Köhler, Stefan; Ames, Friedhelm; Eberhardt, Klaus; Erdmann, Nicole; Funk, Heike; Herrmann, Günter; Kluge, Heinz-Jürgen, et al. First Determination of the Ionization Potential of Americium and Curium. Angew. Chem., Int. Ed. Engl. 1995, 34 (7), 814–15. DOI: 10.1002/anie.199508141.
  6. Carlson, Thomas A.; Nestor, C. W., Jr.; Wasserman, Neil; Mcdowell, J. D. Calculated ionization potentials for multiply charged ions. At. Data Nucl. Data Tables 1970, 2, 63–99. DOI: 10.1016/S0092-640X(70)80005-5.
  7. 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.
  8. 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.
  9. Oetting, F. L.; Rand, M. H.; Ackerman, R. J. The Chemical Thermodynamics of Actinide Elements and Compounds; IAEA: Vienna, 1976; Vol. 1. ISBN 9201490763.
  10. Ghiorso, A.; James, R. A.; Morgan, L. O.; Seaborg, G. T. Preparation of Transplutonium Isotopes by Neutron Irradiation. Phys. Rev. 1950, 78 (4), 472. DOI: 10.1103/PhysRev.78.472.

External links

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