Which of the following best describes the relationship between atomic radius and ionization energy?

• A. Atomic radius and ionization energy are not related.
• B. As atomic radius increases, ionization energy increases.
• C. As atomic radius increases, ionization energy decreases.
• D. Ionization energy remains constant as atomic radius changes.

Answer: (C)

Verified step by step guidance

1. Understand the definitions: Atomic radius is the average distance from the nucleus to the outermost electron, and ionization energy is the energy required to remove an electron from an atom.
2. Recognize the general trend in the periodic table: As atomic radius increases, the outermost electron is farther from the nucleus and experiences less electrostatic attraction.
3. Apply the concept of effective nuclear charge: A larger atomic radius usually means the electron is less tightly held due to increased distance and shielding by inner electrons.
4. Relate this to ionization energy: Because the electron is less tightly held in atoms with larger radii, less energy is required to remove it, so ionization energy decreases as atomic radius increases.
5. Conclude that the correct relationship is: As atomic radius increases, ionization energy decreases.