Chemistry

Question Analysis
This question involves arranging four fourth-period elements by their first ionization energy.
The main focus is on applying the general periodic trend of ionization energy across a period.

Key Concept Explanation
Across a period (left to right), effective nuclear charge increases while atomic radius decreases.
This stronger attraction between the nucleus and valence electrons leads to a general increase in first ionization energy.

Step-by-Step Solution
1. All elements (K, Ca, Sc, Ti) are in Period 4 of the periodic table.
2. Their positions from left to right are: K (Group 1) → Ca (Group 2) → Sc (Group 3) → Ti (Group 4).
3. Apply the period trend: ionization ...