Question

Which of the following has smallest radius?

• A. $1s^{2},2s^{2}2p^{6},3s^{2}$
• B. $1s^{2},2s^{2}2p^{6},3s^{2}3p^{1}$
• C. $1s^{2},2s^{2}2p^{6},3s^{2}3p^{5}$
• D. $1s^{2},2s^{2}2p^{6},3s^{2}3p^{3}$

Answer 1

Answer: (C)

All the elements are of the same periods because all have the equal number of shell. In a period, the size of atom decreases as we from left to right i.e. from $A$ to $ B $ to $D$ to $C$. Hence, element corresponding to C is smallest in the size. Halogen is the smallest atom in a given period of periodic table.