COMEDK · Chemistry · 23. d and f Block Elements

Larger number of oxidation states are exhibited by the actinoids than those of lanthanoids. The reason is:

A Highly reactive nature of the actinoids
B More energy difference between 5f and 6d than between 4f and 5d orbitals
C 4f orbitals are more diffused than 5f orbitals
D Lesser energy difference between 5f and 6d than between 4f and 5d orbitals

Verified Solution

Answer & Solution

Correct Answer

(D) Lesser energy difference between 5f and 6d than between 4f and 5d orbitals

Step-by-step Solution

Detailed explanation

Lanthanoids exhibit primarily the +3 oxidation state because the 4f orbitals are deeply buried within the atom and are shielded by the 5s and 5p orbitals, making them less available for bonding. The energy gap between the 4f and 5d orbitals is relatively large, which restricts…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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