Which of the following best describes the change in ionic radius when a neutral atom becomes a cation?

• A. The ionic radius decreases because the atom loses electrons and the remaining electrons are drawn closer to the nucleus.
• B. The ionic radius remains unchanged because the number of protons and electrons stays the same.
• C. The ionic radius increases because the atom loses electrons, reducing electron-electron repulsion.
• D. The ionic radius increases because the atom gains protons, causing the electrons to spread out.

Answer: (A)

Verified step by step guidance

1. Understand that when a neutral atom becomes a cation, it loses one or more electrons but the number of protons in the nucleus remains the same.
2. Recognize that losing electrons reduces electron-electron repulsion in the electron cloud, allowing the remaining electrons to be pulled closer to the nucleus.
3. Recall that the effective nuclear charge (Z_eff) experienced by the electrons increases because the same positive charge is attracting fewer electrons.
4. Conclude that this increased attraction causes the ionic radius to decrease compared to the neutral atom.
5. Therefore, the best description is that the ionic radius decreases because the atom loses electrons and the remaining electrons are drawn closer to the nucleus.