Difference between revisions of "Fermium"

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==Discovery==
 
==Discovery==
 +
Fermium was first discovered in the fallout from the 'Ivy Mike' nuclear test (1&nbsp;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]], {{Nuclide|Z=94|A=244}}: this could only have formed by the absorption of six [[neutron]]s by a uranium-238 nucleus followed by two [[Beta decay|β<sup>−</sup>&nbsp;decays]].
  
 
==Notes and references==
 
==Notes and references==

Revision as of 09:10, 23 September 2010

einsteiniumfermiummendelevium
Er

Fm

Atomic properties
Atomic number 100
Electron configuration [Rn] 5f12 6s2
Physical properties[1][Note 1]
Melting point 1125 K (850 °C)
Chemical properties[Note 1]
Electronegativity 1.3 (Pauling)
Ionization energy
6.50 eV
627 kJ mol−1
Atomic radii[1][2][3][Note 1]
Metallic radius 196 pm
Ionic radius 92 pm (Fm3+)
Thermodynamic properties[1]
Enthalpy change of atomization 142(13) kJ mol−1
Entropy change of atomization 98(13) J K−1 mol−1
Miscellaneous
CAS number 7440-72-4
Where appropriate, and unless otherwise stated, data are given for 100 kPa (1 bar) and 298.15 K (25 °C).

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.

Notes and references

Notes

  1. 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. 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.
  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.
  3. 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.

Further reading

External links

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