Semi-empirical Calculations on the Free Energy and Enthalpy of Hydration for the Trivalent Lanthanides and Actinides

An electrostatic hydration model, that had previously been developed for ions of the noble–gas structure, was applied to the trivalent lanthanide and trivalent actinide ions. For the trivalent lanthanides it was found that a single primary hydration number resulted in a satisfactory fit of the model to the experimental free energy and enthalpy data. Subsequently, the model was applied to the trivalent actinide ions with a view to predicting values for the free energy and enthalpy of hydration for this series. A primary hydration number for the actinide series was determined by fitting the model to existing experimental enthalpy data for Pu3+. The predictions for this series were found to compare favorably with the few experimental and estimated values that exist.