8.20 Compare the chemistry of actinoids with that of the lanthanoids, with special reference to:
(iii) oxidation state
The principle oxidation states of lanthanoids are +3, but sometimes they also show +2 and +4 oxidation states. This is due to the extra stability of fully-filled and half-filled orbitals.
Actinoids have a greater range of oxidation states due to their comparable energies, and they also have the principle that their oxidation state is +3, but they have more compounds in +3 oxidation states than lanthanoids.