Larger number of oxidation states are exhibited by the actinoids than those by the lanthanoids, the main reason being
- Lesser energy difference between 5f and 6d than between 4f and 5d orbitals
- More energy difference between 5f and 6d than between 4f and 5d orbitals
- More reactive nature of the actinoids than the lanthanoids
- 4f orbitals more diffused than the 5f orbitals
Actinoids show different oxidation states such as +2, +3, +4, +5, +6 and +7. However +3 oxidation state is most common among all the actinoids.
The wide range of oxidation states of actinoids is attributed to the fact that the 5f, 6d and 7s energy levels are of comparable energies.
Therefore, all these three subshells can participate.
The correct option is A.