Question

Which ranks the following atoms $(Li,Na,K,Rb)$ from the smallest to largest atomic radius?

• A. $Li<Na<K<Rb$
• B. $Rb<K<Na<Li$
• C. $K<Na<Li<Rb$
• D. $Na<Li<Rb<K$

Answer 1

The correct option is A $Li<Na<K<Rb$

The given elements belong to the same group (IA) in the periodic table. The atomic size increases down the group due to an addition of new shells.

Hence the order of size is $Li<Na<K<Rb$.

Hence, the correct option is $\text{A}$