Chemistry

Question Analysis
This question involves applying the period trend to identify an element within a specific radius range.
The main focus is on ordering Period 3 elements by atomic radius and finding the missing element in the sequence.

Key Concept Explanation
Across Period 3 (left to right), atomic radius decreases in the order: Na > Mg > Al > Si > P > S > Cl.
Each element has a higher nuclear charge than the one to its left, pulling the electron cloud closer and reducing the atomic radius.

Step-by-Step Solution
1. Recall the full atomic radius order of Period 3 elements.
2. Locate S ...