Which of the following best explains why an increase in atomic radius generally results in a lower ionization energy?

• A. A larger atomic radius means the nucleus has a stronger hold on the valence electrons, increasing ionization energy.
• B. As atomic radius increases, the number of protons decreases, making it harder to remove an electron.
• C. An increase in atomic radius causes more electron-electron repulsion, which increases ionization energy.
• D. The valence electrons are farther from the nucleus and experience less electrostatic attraction, making them easier to remove.

Answer: (D)

Verified step by step guidance

1. Understand the concept of atomic radius: It is the average distance from the nucleus to the outermost electrons in an atom.
2. Recall that ionization energy is the energy required to remove an electron from an atom in its gaseous state.
3. Recognize that as atomic radius increases, the valence electrons are located farther from the nucleus.
4. Apply Coulomb's law, which states that the electrostatic attraction between the positively charged nucleus and negatively charged electrons decreases with increasing distance.
5. Conclude that because the valence electrons are farther away, they experience less attraction to the nucleus, making them easier to remove and thus lowering the ionization energy.