Chemistry

Question Analysis
This question involves applying the group trend to a subset of Group 2 elements to identify the one with the lowest first ionization energy.
The main focus is on using the top-to-bottom trend for specific alkaline earth metals.

Key Concept Explanation
First ionization energy decreases down a main group. For Group 2 elements, the lower the element is in the group, the larger its atomic radius and the weaker the hold on its valence electrons, resulting in a lower ionization energy.

Step-by-Step Solution
1. Recall the Group 2 order: Be (top) → Mg → Ca (bottom, among the options).
2. Apply the group trend: ionization energy decreases down the group.