Patterns in Hydration Energies Enthalpies for the Lanthanide Ions

8 Patterns in Hydration Energies (Enthalpies) for the Lanthanide Ions 

Metallic and ionic radii across the lanthanide series. 

9 Enthalpy Changes for the Formation of Simple Lanthanide Compounds 

Observed patterns of chemical behaviour can sometimes appear confusing or sometimes just be encapsulated in rules [e.g. Ce has a stable (+4) oxidation state]. They can frequently be explained in terms of the energy changes involved in the processes. 

Among the fluorides, lanthanum forms only LaFs, whilst cerium forms CeFs and CeF4. (Tetrafluorides are also known for Pr and Tb, see Section 3.4). Why do neighbouring metals behave so differently First, examine the energetics of formation of LaFs using a Bom-Haber cycle. 

---