Why does the atomic radius increase as you go from the top to the bottom of a chemical family in the periodic table?

• A. Because the atoms gain more neutrons, which increases the size of the electron cloud.
• B. Because electrons are removed from the atom, making it larger.
• C. Because the number of protons decreases, reducing the nuclear charge.
• D. Because additional electron shells are added, increasing the distance between the nucleus and the outermost electrons.

Answer: (D)

Verified step by step guidance

1. Understand that atomic radius refers to the size of an atom, typically measured from the nucleus to the outer boundary of the electron cloud.
2. Recognize that as you move down a group (family) in the periodic table, each successive element has an additional electron shell compared to the one above it.
3. Know that adding more electron shells increases the distance between the nucleus and the outermost electrons, which causes the atomic radius to increase.
4. Consider that although the number of protons (nuclear charge) also increases down a group, the effect of increased electron shielding from inner shells reduces the effective nuclear attraction on the outer electrons.
5. Conclude that the dominant factor for the increase in atomic radius down a group is the addition of electron shells, which outweighs the increased nuclear charge and results in a larger atomic size.