Question

Actinoids show larger number of oxidation states:

• A. because they are electropositive in nature
• B. because they have large atomic numbers
• C. because they have large atomic size
• D. due to comparable energies of 5f, 6d and 7s orbitals

Hint:

{Key Difference:} Lanthanoids → mostly +3 oxidation state Actinoids → variable oxidation states due to participation of 5f, 6d, and 7s orbitals.

Answer 1

The Correct Option is D

Concept: Actinoids exhibit a wide range of oxidation states due to the involvement of multiple orbitals in bonding. Unlike lanthanoids, actinoids have:

• Partially filled 5f orbitals
• Accessible 6d orbitals
• Outer 7s electrons

Because the energies of these orbitals are very close, electrons from all three can participate in bonding.
Step 1: Analyze the reason. When orbitals of similar energy levels are available, multiple electrons can be lost or shared, leading to variable oxidation states.
Step 2: Evaluate options.

• Electropositivity — not the main reason.
• Large atomic number — not directly related to oxidation states.
• Large atomic size — minor factor.
• Comparable energies of 5f, 6d, 7s orbitals — correct reason.

Step 3: Conclusion. \[ \therefore \text{Correct answer = (D)} \]