How does increasing the number of energy levels (principal quantum number, n) affect the atomic radius of an atom?

• A. The atomic radius decreases as the number of energy levels increases.
• B. The atomic radius remains unchanged as the number of energy levels increases.
• C. The atomic radius first increases and then decreases as the number of energy levels increases.
• D. The atomic radius increases as the number of energy levels increases.

Answer: (D)

Verified step by step guidance

1. Understand that the atomic radius is the average distance from the nucleus to the outermost electron in an atom.
2. Recall that the principal quantum number \(n\) represents the energy level or shell in which an electron resides; as \(n\) increases, electrons occupy shells farther from the nucleus.
3. Recognize that adding more energy levels means electrons are located in shells that are progressively farther from the nucleus, which generally increases the size of the electron cloud.
4. Consider the effect of electron shielding, where inner electrons partially block the attraction between the nucleus and outer electrons, allowing outer electrons to be less tightly held and thus increasing atomic radius.
5. Conclude that as the number of energy levels (\(n\)) increases, the atomic radius increases because electrons are found in shells farther from the nucleus and experience more shielding.