Final answer:
Cations with larger charges are smaller than cations with smaller charges. The size of ions can also be affected by the number of electrons compared to the neutral atom. When comparing cations with the same charge, the ion with a higher atomic number generally has a larger radius.
Step-by-step explanation:
Cations with larger charges are smaller than cations with smaller charges. Proceeding down the groups of the periodic table, cations of successive elements with the same charge generally have larger radii, corresponding to an increase in the principal quantum number, n. For example, V²+ has an ionic radius of 79 pm, while that of V³+ is 64 pm.
Additionally, the radius of an ion can be affected by the number of electrons it has compared to the neutral atom. The removal of electrons results in an ion that is smaller than the parent element, while the addition of electrons results in an ion that is larger than the parent atom. For example, the rubidium ion, Rb+, is smaller than the rubidium atom, and the tellurium ion, Te²-, is larger than the tellurium atom. Similarly, the oxygen anion, O2, is larger than the fluoride anion, F2.
Furthermore, when comparing cations with the same charge, the ion with a higher atomic number generally has a larger radius. For example, the sodium cation, Na+, is larger than the magnesium cation, Mg2+.