Actinium

Atomic properties
Atomic number	89
Electron configuration	[Rn] 6d1 7s2
Physical properties
Melting point	1050 °C (1350 K)
Boiling point	3300 °C (3600 K)
Density	10.07 g cm−3
Chemical properties
Electronegativity	1.3 (Pauling)
Ionization energies
1st	5.17(12) eV; 499(12) kJ mol−1
2nd	12.06 eV; 1164 kJ mol−1
Atomic radii
Covalent radius	215 pm
Metallic radius	188 pm
Ionic radius	126 pm (Ac3+, Oh)
Thermodynamic properties
Enthalpy change of atomization	406 kJ mol−1
Enthalpy change of fusion	10.5 kJ mol−1
Enthalpy change of vaporization	293 kJ mol−1
Miscellaneous
CAS number	7440-34-8
	Where appropriate, and unless otherwise stated, data are given for 100 kPa (1 bar) and 298.15 K (25 °C).
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radium ← actinium → thorium

La
↑
Ac
↓
—

Actinium (symbol: Ac) is a chemical element, one of the transition metals and also an actinoid. All isotopes of actinium are unstable, with half-lives of less than 22 years:^[8] however, actinium-227 (t_½ = 21.772(3) a) is formed as a decay product of uranium-235 (t_½ = 704(1) × 10⁶ a) and so small amounts of actinium are present in all samples of natural uranium.

Notes and references

Notes

↑ ^1.0 ^1.1 Many of the properties of actinium are only known through estimation and/or extrapolation. Several estimates of the melting point and thermodynamic properties have been made; the boiling point was estimated on the basis of vapour pressure measurements; the electronegativity was estimated on the basis of periodic trends. The density and ionic radii were directly determined.

References

↑ ^1.0 ^1.1 Kirby, H. W.; Morss, L. R. Actinium. 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. 1, Chapter 2, pp 18–51. doi:10.1007/1-4020-3598-5_2, <http://radchem.nevada.edu/classes/rdch710/files/actinium.pdf>.
↑ Pauling, Linus The Nature of the Chemical Bond, 3rd ed.; Ithaca, NY, 1960. ISBN 0-8014-0333-2.
↑ Sugar, Jack Ionization energies of the neutral actinides. J. Chem. Phys. 1973, 59, 788–91. DOI: 10.1063/1.1680091. Sugar, Jack Revised ionization energies of the neutral actinides. J. Chem. Phys. 1974, 60, 4103. DOI: 10.1063/1.1680874.
↑ Moore, Charlotte E. Ionization potentials and ionization limits derived from the analyses of optical spectra. Natl. Stand. Ref. Data Ser., (U.S. Natl. Bur. Stand.) 1970, 34, 1–22, <http://www.nist.gov/data/nsrds/NSRDS-NBS34.pdf>.
↑ 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.
↑ 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.
↑ Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1102–10. ISBN 0-08-022057-6.
↑ Audi, G.; Bersillon, O.; Blachot, J.; Wapstra, A. H. The NUBASE evaluation of nuclear and decay properties. Nucl. Phys. A 2003, 729, 3–128. doi:10.1016/j.nuclphysa.2003.11.001, <http://amdc.in2p3.fr/nubase/Nubase2003.pdf>.

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[est-2] 1.0 ^1.1 Many of the properties of actinium are only known through estimation and/or extrapolation. Several estimates of the melting point and thermodynamic properties have been made; the boiling point was estimated on the basis of vapour pressure measurements; the electronegativity was estimated on the basis of periodic trends. The density and ionic radii were directly determined.

[K.26M-1] 1.0 ^1.1 Kirby, H. W.; Morss, L. R. Actinium. 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. 1, Chapter 2, pp 18–51. doi:10.1007/1-4020-3598-5_2, <http://radchem.nevada.edu/classes/rdch710/files/actinium.pdf>.

[3] Pauling, Linus The Nature of the Chemical Bond, 3rd ed.; Ithaca, NY, 1960. ISBN 0-8014-0333-2.

[4] Sugar, Jack Ionization energies of the neutral actinides. J. Chem. Phys. 1973, 59, 788–91. DOI: 10.1063/1.1680091. Sugar, Jack Revised ionization energies of the neutral actinides. J. Chem. Phys. 1974, 60, 4103. DOI: 10.1063/1.1680874.

[5] Moore, Charlotte E. Ionization potentials and ionization limits derived from the analyses of optical spectra. Natl. Stand. Ref. Data Ser., (U.S. Natl. Bur. Stand.) 1970, 34, 1–22, <http://www.nist.gov/data/nsrds/NSRDS-NBS34.pdf>.

[6] 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.

[7] 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.

[G.26E-8] Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1102–10. ISBN 0-08-022057-6.

[NUBASE-9] Audi, G.; Bersillon, O.; Blachot, J.; Wapstra, A. H. The NUBASE evaluation of nuclear and decay properties. Nucl. Phys. A 2003, 729, 3–128. doi:10.1016/j.nuclphysa.2003.11.001, <http://amdc.in2p3.fr/nubase/Nubase2003.pdf>.

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Actinium

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