Which of the following factors contributes to the increased ionic radius of an anion compared to its parent atom?

• A. Addition of electrons increases electron-electron repulsion, causing the electron cloud to expand.
• B. Formation of an anion results in a decrease in principal quantum number.
• C. Loss of electrons leads to a decrease in shielding effect.
• D. Increase in nuclear charge pulls electrons closer to the nucleus.

Answer: (A)

Verified step by step guidance

1. Understand that when an atom gains electrons to form an anion, the number of electrons increases while the number of protons in the nucleus remains the same.
2. Recognize that the addition of electrons increases electron-electron repulsion within the electron cloud, causing the electrons to spread out more to minimize repulsion.
3. Recall that the principal quantum number (n) does not decrease when an anion forms; it remains the same because electrons are added to the same energy level or shell.
4. Note that loss of electrons would decrease shielding, but in the case of an anion, electrons are added, so shielding actually increases or remains similar, not decreases.
5. Understand that the nuclear charge (number of protons) does not increase when forming an anion, so it does not pull electrons closer; instead, the increased repulsion causes the electron cloud to expand, increasing the ionic radius.