As you move down a group (family) on the periodic table, what happens to the atomic radius of the elements?

• A. The atomic radius decreases.
• B. The atomic radius remains the same.
• C. The atomic radius increases.
• D. The atomic radius first increases, then decreases.

Answer: (C)

Verified step by step guidance

1. Understand that the atomic radius is the average distance from the nucleus to the outermost electrons in an atom.
2. Recognize that as you move down a group in the periodic table, each successive element has an additional electron shell (energy level) compared to the one above it.
3. Since each new electron shell is farther from the nucleus, the size of the electron cloud increases, which tends to increase the atomic radius.
4. Consider the effect of increased nuclear charge (more protons) as you move down the group, but note that the shielding effect from inner electrons reduces the effective nuclear attraction on the outermost electrons.
5. Conclude that because the shielding effect outweighs the increased nuclear charge, the atomic radius increases as you move down a group in the periodic table.