Chemistry

Question Analysis
This question tests the basic definition of first ionization energy. The main focus is on recalling the key terms and concepts in the definition.

Key Concept Explanation
Ionization energy is an endothermic process—it requires energy to remove an electron from an atom (energy is not released). The "first" ionization energy specifically refers to removing the outermost (valence) electron from a neutral gaseous atom.

Step-by-Step Solution
1. Eliminate options that describe energy release (A and D)—ionization requires energy, it does not release it.
2. Eliminate option C—it describes removing all valence electrons, not just the first one.
3. Option B matches the correct definition: energy required to remove ...