Chemistry

Question Analysis
This question tests the ability to compare the atomic radii of two elements in the same group and explain the reason for the difference based on periodic trends.

Key Concept Explanation
Magnesium (Mg) and calcium (Ca) are in the same group (Group 2) but different periods. Calcium is in the next period and has an additional electron shell, which increases the distance from the nucleus to the outermost electrons. The increased electron shielding in Ca also contributes to the larger atomic radius.

Step-by-step Solution
1. Identify the elements: Mg and Ca.
2. Determine their positions in the periodic table: both in Group 2, but Ca is in the next period.
3. Explain the reason: Ca has an additional electron shell, which increases the distance from the nucleus to the outermost electrons.
4. Mention the effect of electron shie...