COMPARATIVE SOLUTION CHEMISTRY OF THE 4F AND 5F ELEMENTS

The chemical behaviors of the lanthanide 4f and 5f elements are compared for similarities and differences. The relative stabilities are compared for the II, III, and IV oxidation states and are discussed in terms of the differences in the relative energies of the nf, (n+1)d and (n+2)p orbitals (n=4 and 5). Comparisons of the degree of inner sphere hydration and the thermodynamics of hydration as well as the rates of solvolysis and preferential solvation in mixed solvents are discussed. The thermodynamics of complexation of both families are compared and interpreted. A principal focus is the interpretation of such data in terms of relative degrees of covalency in the two families. The validity of the use of appropriate 4f elements as chemical analogs of the 5f elements is reviewed.