Question

Identify the factor responsible for the greater range of oxidation states in actinoids.

• A. actinoid contraction
• B. radioactive nature of actinoids
• C. 5f, 6d and 7s levels having comparable energies
• D. 4f and 5d levels being close in energies

Hint:

More sub-shells of similar energy give more oxidation states.

Answer 1

The Correct Option is C

Step 1: Link:
More available electrons means more possible oxidation states.

Step 2: Energy gap:
For actinoids, the $5f$ orbitals are less buried than $4f$ in lanthanoids, so $5f$, $6d$ and $7s$ lie close. Electrons from all of them can be removed.

Step 3: Elimination:
Size contraction and radioactivity are not about electron availability. $4f$/$5d$ closeness is a lanthanoid feature. So choose (C).

Final Answer:
The close spacing of 5f, 6d and 7s gives many oxidation states. \[ \boxed{C} \]