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Lanthanides: Variable Valency

  1. Andrew W.G. Platt

Published Online: 17 DEC 2012

DOI: 10.1002/9781119951438.eibc2010

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Platt, A. W. 2012. Lanthanides: Variable Valency. Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. Staffordshire University, Stoke-on-Trent, UK

Publication History

  1. Published Online: 17 DEC 2012

Abstract

The reasons for the restricted range of oxidation states of lanthanides are explained with emphasis on the relative unimportance of covalent bonding. The stability of the +2 and +4 oxidation states of the metals is discussed in terms of the thermodynamics of their formation and decomposition reactions in the solid state and in solution. Stability of LnIV and LnII in the solid state is assessed with respect to decomposition to LnIII and disproportionation to LnIII and Ln0, respectively. The thermodynamic instability of all LnIV and LnII species in aqueous solution is explained by appropriate redox potentials. The kinetic stability for some CeIV and TbIV species in aqueous solution is discussed and the variation of oxidizing ability of CeIV as a function of counterion outlined. Redox data in nonaqueous systems are briefly discussed.

Keywords:

  • lanthanide oxidation states;
  • reduction potentials;
  • thermochemical cycles;
  • solution stability;
  • solid-state stability;
  • variable valency