Actinium

Atomic properties
Atomic number	89
Electron configuration	[Rn] 6d1 7s2
Physical properties
Melting point	817 °C (1090 K)
Boiling point	2470 °C (2743 K)
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
Ionic radius	126 pm (Ac3+, Oh)
Thermodynamic properties
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.

Notes and references

↑ ^1.0 ^1.1 Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1102–10. ISBN 0-08-022057-6.
↑ 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.

See also the corresponding article on Wikipedia.

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