Kaplan Nursing Entrance Practice Exam

What happens to the ionization energy as atomic radius decreases?

1. It increases

2. It stays the same

3. It decreases

4. It fluctuates

The correct answer is: It increases

As atomic radius decreases, ionization energy increases. This phenomenon is primarily due to the fact that a smaller atomic radius indicates that the electrons are closer to the nucleus. The positively charged protons in the nucleus exert a stronger attractive force on the negatively charged electrons when they are nearer to each other. This stronger attraction means that more energy is required to remove an electron from the atom. If the atomic radius were larger, the outer electrons would be farther from the nucleus and experience less pull from it, making them easier to remove and resulting in lower ionization energy. Therefore, as the radius shrinks, the energy needed to ionize the atom rises, demonstrating the direct relationship between decreased atomic radius and increased ionization energy.