Question

The main reason for larger number of oxidation states exhibited by the actinoids than the corresponding lanthanoids, is:

• A. the lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitals
• B. more energy difference between 5f and 6d orbitals than between 4f and 5d orbitals
• C. greater reactive nature of the actinoids than the lanthanoids
• D. larger atomic size of actinoids than the lanthanoids

Answer 1

The correct option is A the lesser energy difference between 5f and 6d orbitals than between 4f and 5d orbitals

Actinoids shows larger oxidation states due to poor shielding of both $4f$ and $5f$ orbital electrons as a result these orbital have almost similar energy and hence take part in bond formation. Also, there is very small energy between $5f,6d$ and $7s$ subshells.