As you move down a column in the periodic table, how does the ionic radius of cations with the same charge change?

• A. The ionic radius first increases, then decreases.
• B. The ionic radius decreases because nuclear charge increases.
• C. The ionic radius increases due to the addition of electron shells.
• D. The ionic radius remains constant.

Answer: (C)

Verified step by step guidance

1. Identify the trend being asked about: the change in ionic radius of cations with the same charge as you move down a group (column) in the periodic table.
2. Recall that moving down a group means moving to elements with higher principal quantum numbers (n), which means more electron shells are added.
3. Understand that adding more electron shells increases the distance between the nucleus and the outermost electrons, generally increasing the size of the ion.
4. Consider that although nuclear charge increases down the group, the effect of added electron shells (increased shielding) outweighs the increased nuclear charge, leading to a larger ionic radius.
5. Conclude that for cations with the same charge, the ionic radius increases as you move down a column due to the addition of electron shells.