Compared to their respective neutral atoms, how do the ionic radii of a divalent cation and a monovalent anion typically change?

• A. The divalent cation has a smaller radius than its neutral atom, while the monovalent anion has a larger radius than its neutral atom.
• B. Both the divalent cation and the monovalent anion have smaller radii than their neutral atoms.
• C. The divalent cation has a larger radius than its neutral atom, while the monovalent anion has a smaller radius than its neutral atom.
• D. Both the divalent cation and the monovalent anion have larger radii than their neutral atoms.

Answer: (A)

Verified step by step guidance

1. Recall that the ionic radius depends on the number of electrons and the effective nuclear charge experienced by those electrons in an ion compared to its neutral atom.
2. For a divalent cation (an ion with a +2 charge), the atom loses two electrons. This reduces electron-electron repulsion and increases the effective nuclear charge per electron, causing the electrons to be pulled closer to the nucleus.
3. Therefore, the ionic radius of a divalent cation is smaller than that of its neutral atom because the remaining electrons are held more tightly.
4. For a monovalent anion (an ion with a -1 charge), the atom gains one electron. This increases electron-electron repulsion and decreases the effective nuclear charge per electron, causing the electron cloud to expand.
5. Thus, the ionic radius of a monovalent anion is larger than that of its neutral atom because the added electron causes the electron cloud to spread out.