Chemistry

Question Analysis
This question evaluates the understanding of periodic trends, specifically the trend of atomic radius across a period.

Key Concept Explanation
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 elements in Period 4: K, Ca, Sc, and Ti.
2. Compare their positions in the periodic table: K (Group 1), Ca (Group 2), Sc (Group 3), and Ti (Group 4).
3. As you move from left to right across a period, ...