Question

Arrange the following elements in order of decreasing atomic size.

• A. Nitrogen (N)
• B. Carbon (C)
• C. Phosphorus (P)
• D. Sulphur (S)

Answer 1

Down a group: The increase in number of valence shells overcomes the increased nuclear charge. Hence, atomic size increases.

Across a period: Number of valence shells remain the same which cannot overcome the increased nuclear charge. Hence, atomic size decreases from left to right in a period.
$$\begin{array}{ccc}\text{14}& \text{15}& \text{16}\\ \text{C}& \text{N}& \\ & \text{P}& \text{S}\end{array}$$

So, the correct order of atomic size is as follows:
P > S > C > N