to Lanthanides & Actinides Menu
  << BACK TO MENU | PERIODIC TABLE >>BibliographyBIBLIOGRAPHY
Lanthanides & Actinides
Actinide Oxidation States

Survey of Actinide Oxidation States

The known oxidation states of the actinides are indicated and surveyed:

**importance: > >

7

6

5

4

3
2

Ac
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr

+2

  • Unusual oxidation state
  • Common only for the heaviest elements
  • No2+ & Md2+ are more stable than Eu2+
  • Actinide An2+ ions have similar properties to Lanthanide Ln2+ and to Ba2+ ions
  • rationalization of stabilities: Open University Course Book p. 54-56

+3

  • The most common oxidation state
  • The most stable oxidation state for all trans-Americium elements (except No?)
  • Of marginal stability for early actinides Th, Pa, U (But: Group oxidation state for Ac)
  • General properties resemble Ln3+ and are size-dependent
    • stability constants of complex formation are similar for same size An3+ & Ln3+
    • isomorphism is common
    • later An3+ & Ln3+ must be separated by ion-exchange/solvent extraction
  • Binary Halides, MX3 easily prepared, & easily hydrolysed to MOX
  • Binary Oxides, M2O3 known for Ac, Th and trans-Am elements

+4

  • Principal oxidation state for Th
    Th4+ chemistry shows resemblance to Zr4+ / Hf4+ - is it a transition metal?
  • Very important, stable state for Pa, U, Pu
  • Am, Cm, Bk & Cf are increasingly easily reduced - only stable in certain complexes
    e.g. Bk4+ is more oxidizing than Ce4+
  • MO2 known from Th to Cf (fluorite structure)
  • MF4 are isostructural with lanthanide tetrafluorides
  • MCl4 only known for Th, Pa, U & Np
  • Hydrolysis / Complexation / Disproportionation are all important in (aq)

+5

  • Principal state for Pa
    Pa5+ chemistry resembles that of Nb5+ / Ta5+ - is it a transition metal?
  • For U, Np, Pu and Am the AnO2+ ion is known (i.e. quite unlike Nb/Ta)
  • Comparatively few other AnV species are known
    e.g. fluorides, PaF5, NbF5, UF5; fluoro-anions, AnF6-, AnF72-, AnF83-

    e.g. oxochlorides, PaOCl3, UOCl3; uranates, NaUO3

+6

  • AnO22+ ions are important for U, Np, Pu, Am
    UO22+ is the most stable
  • Few other compoundse.g. AnF6 (An = U, Np, Pu), UCl6, UOF4etc... , U(OR)6

+7

  • Only the marginally stable oxo-anions of Np and Pu, e.g. AnO53-

--Info & DownloadsBibliography  [textbook & online resources]

Source: Dr. S.J. Heyes; University of Oxford
      << BACK TO MENU | PERIODIC TABLE | MEMBERSHIP | HOME >>Top of Page
Join Today!
.:: Radiochemistry.org© - 2003 ::.