Which of the following best explains why smaller atoms generally have higher ionization energies?

• A. Electrons in smaller atoms are closer to the nucleus and experience a stronger electrostatic attraction, making them harder to remove.
• B. Smaller atoms have lower nuclear charge, so electrons are held more tightly.
• C. Electrons in smaller atoms are farther from the nucleus, so they require more energy to remove.
• D. Smaller atoms have more electron shells, which increases the shielding effect and makes electrons harder to remove.

Answer: (A)

Verified step by step guidance

1. Understand that ionization energy is the energy required to remove an electron from an atom in its gaseous state.
2. Recall that the strength of the electrostatic attraction between the nucleus and electrons depends on the distance between them and the effective nuclear charge experienced by the electrons.
3. Recognize that smaller atoms have electrons that are closer to the nucleus, which means the electrostatic attraction is stronger due to shorter distance.
4. Consider that stronger attraction between the nucleus and electrons means more energy is needed to remove an electron, resulting in higher ionization energy.
5. Note that other options are incorrect because smaller atoms do not have lower nuclear charge, electrons are not farther from the nucleus, and smaller atoms have fewer electron shells, which reduces shielding rather than increasing it.