Chemistry

Question Analysis
This question tests the student's ability to arrange elements in a given period in order of decreasing atomic radius based on their position in the periodic table.

Key Concept Explanation
In a given period, the atomic radius decreases as you move from left to right due to the increasing nuclear charge, which pulls the valence electrons closer to the nucleus. The elements listed (Na, Mg, Al, Si) are all in Period 3, so the atomic radius decreases from Na to Si.

Step-by-step Solution
1. Identify the elements: Sodium (Na), Magnesium (Mg), Aluminum (Al), Silicon (Si).
2. Determine their positions in the periodic table: all in Period 3, from left to right.
3....