Question

Due to lanthanide contraction

• A. Fe, Co, Ni have equal size
• B. Zr and Hf have equal size
• C. all f-block ions have equal size
• D. all isoelectronic ions have equal size

Hint:

Lanthanide contraction causes elements of 4d and 5d series to have similar sizes.

Answer 1

The Correct Option is B

Understanding the Concept: Lanthanide contraction is the gradual decrease in atomic size across lanthanide series due to poor shielding of f-electrons.

Step 1: Effect on elements
Zr (4d) and Hf (5d) have nearly same atomic size due to contraction.

Step 2: Reason
Extra electrons in f-orbitals do not shield effectively → nucleus pulls electrons closer. Final Answer:
Thus, Zr and Hf have almost equal size.