Actinium

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radium ← actinium → thorium
La
↑
Ac
↓
—
Atomic properties
Atomic number 89
Electron configuration [Rn] 6d1 7s2
Physical properties[1][note 1]
Melting point 1050 °C (1350 K)
Boiling point 3300 °C (3600 K)
Density 10.07 g cm−3
Chemical properties[2][note 1]
Electronegativity 1.3 (Pauling)
Ionization energies[3][4]
1st 5.17(12) eV
499(12) kJ mol−1
2nd 12.06 eV
1164 kJ mol−1
Atomic radii[1][5][6]
Covalent radius 215 pm
Metallic radius 188 pm
Ionic radius 126 pm (Ac3+, Oh)
Thermodynamic properties[1][7]
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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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 (t½ = 21.772(3) a) is formed as a decay product of uranium-235 (t½ = 704(1) × 106 a) and so small amounts of actinium are present in all samples of natural uranium.

Discovery

The story of the discovery of actinium has generated a certain amount of controversy.[1][9][10] Credit is usually given to French chemist André-Louis Debierne, who described a new source of radiation from pitchblende in 1899,[11] with further details in 1900.[12] He named the new element actinium,[12] from the Greek ἀκτίς, aktis (genitive: ἀκτίνος, aktinos) meaning "ray".

The German chemist Friedrich Giesel was also studying the composition of pitchblende, and described a new source of radiation in 1902,[13] with further details in 1903.[14] Giesel called his new element emanium, from "emanation".[15]

Notes and references

Notes

  1. ↑ 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 determined by X-ray crystallography.

References

  1. ↑ 1.0 1.1 1.2 1.3 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>.
  2. ↑ Pauling, Linus The Nature of the Chemical Bond, 3rd ed.; Ithaca, NY, 1960. ISBN 0-8014-0333-2.
  3. ↑ 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.
  4. ↑ 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>.
  5. ↑ 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.
  6. ↑ 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.
  7. ↑ Greenwood, Norman N.; Earnshaw, A. Chemistry of the Elements; Pergamon: Oxford, 1984; pp 1102–10. ISBN 0-08-022057-6.
  8. ↑ 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>.
  9. ↑ Kirby, H. W. The Discovery of Actinium. Isis 1971, 62 (3), 290–308. DOI: 10.1086/350760.
  10. ↑ Adloff, J. P. The centenary of a controversial discovery: actinium. Radiochim. Acta 2000, 88, 123–28. DOI: 10.1524/ract.2000.88.3-4.123.
  11. ↑ Debierne, A. Sur un nouvelle matière radio-active. C. R. Hebd. Seances Acad. Sci. 1899, 129, 593–95, <http://gallica.bnf.fr/ark:/12148/bpt6k3085b/f593.table>.
  12. ↑ 12.0 12.1 Debierne, A. Sur un nouvelle matière radio-actif – l'actinium. C. R. Hebd. Seances Acad. Sci. 1900, 130, 906–8, <http://gallica.bnf.fr/ark:/12148/bpt6k3086n/f906.table>.
  13. ↑ Giesel, F. Ueber Radium und radioactive Stoffe. Ber. Dtsch. Chem. Ges. 1902, 35, 3608–11. DOI: 10.1002/cber.190203503187.
  14. ↑ Giesel, F. Ueber den Emanationskörper aus Pechblende und über Radium. Ber. Dtsch. Chem. Ges. 1903, 36 (1), 342–47. DOI: 10.1002/cber.19030360177.
  15. ↑ Giesel, F. Ueber den Emanationskörper (Emanium). Ber. Dtsch. Chem. Ges. 1904, 37 (2), 1696–99. DOI: 10.1002/cber.19040370280.

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