Fermium

Atomic properties
Atomic number	100
Electron configuration	[Rn] 5f12 6s2
Physical properties
Melting point	1125 K (850 °C)
Chemical properties
Electronegativity	1.3 (Pauling)
Ionization energy
	6.50 eV; 627 kJ mol−1
Atomic radii
Metallic radius	196 pm
Ionic radius	92 pm (Fm3+)
Thermodynamic properties
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).
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einsteinium ← fermium → mendelevium

Er
↑
Fm
↓
–

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

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.

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[est-2] 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.

[H.26G-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.

[3] 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.

[4] 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.

[1]

[Note 1]

[2]

[3]

Fermium

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Notes

References

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