Chemistry

Question Analysis
This question evaluates the student's understanding of the periodic trend in atomic radius across a period and their ability to provide a specific example to support their explanation.

Key Concept Explanation
The atomic radius generally decreases as you move from left to right across a period due to the increasing nuclear charge, which pulls the valence electrons closer to the nucleus.

Step-by-step Solution
1. Identify the trend: Atomic radius decreases from left to right across a period.
2. Explain the reason: Increasing nuclear charge (more protons) pulls valence electrons closer to the nucleus.
3. Provide a specific example: In Period 3, the atomic radius of sodium (Na) is larger than that of chlorine (Cl).
4. Therefore, the correct answer is: As you move from left to right across a period, the atomic radius generally decreases. This is because the number o...