Question

Largest difference in radii is found in which of the following pair?

• A. $Li,Na$
• B. $Na,K$
• C. $K,Rb$
• D. $Rb,Cs$

Answer 1

Answer: (B)

$Na,K$

Radii of atoms increase as we go down the group due to the addition of extra energy shell. The nuclear charge also increases on moving down the group but the influence of addition of energy shell predominates. This predomination is larger in case when we move from $Na$ to $K$ among all the options given.

Hence, option $B$ is correct.