Question

Which of the following pair/s have nearly same size?

• A. $Zr,Hf$
• B. $Nb,Ta$
• C. $Fe,Zn$
• D. $K,Rb$

Answer 1

Answer: (A), (B)

The correct options are
A $Zr,Hf$
B $Nb,Ta$

Due to lanthanide contraction, the size of second and third transition series are nearly same. It is due to increase in nulcear charge by 32 units except for Y and La.
$Zr\simeq Hf,Nb\simeq Ta$