More number of oxidation states are exhibited by the actinoids than...

Actinides exhibit more number of oxidation states than lanthanides because of lesser energy difference between the $5 f$ and $6 d$ orbitals than that between the $4 f$ and $5 d$ orbitals. Related Theory Actinides have a very small energy gap between $5 f$ and $6 d$ orbitals, so they can easily form a variety of configurations and hence they are found to be stable in various oxidation states. Lanthanides are comparatively less electropositive than actinides and due to that reason, they are less reactive than actinides.