Chemistry

Question Analysis
This question tests knowledge of the basic periodic trend of first ionization energy across a period. The main focus is on recalling the fundamental left-to-right trend for main-group elements.

Key Concept Explanation
Across a period, the number of protons in the nucleus (nuclear charge) increases, but the number of inner electron shells stays the same. This increases the effective nuclear charge, pulling valence electrons closer to the nucleus. More energy is needed to remove an electron, so ionization energy increases left to right.

Step-by-Step Solution
1. Recall the definition of a period (horizontal row on the periodic table).
2. Remember ...