Which of the following best describes how atomic radius changes as one goes down vertically in a group in the periodic table?

• A. Atomic radius increases due to the addition of electron shells.
• B. Atomic radius fluctuates unpredictably due to electron repulsion.
• C. Atomic radius decreases because nuclear charge increases.
• D. Atomic radius remains constant because the number of valence electrons does not change.

Answer: (A)

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. Recall that as you move down a group (column) in the periodic table, each successive element has an additional electron shell compared to the one above it.
3. Recognize that adding more electron shells increases the distance between the nucleus and the outermost electrons, which generally causes the atomic radius to increase.
4. Consider the effect of nuclear charge: although the number of protons increases down the group, the added inner electron shells shield the outer electrons from the full nuclear charge, reducing the effective nuclear attraction on the outermost electrons.
5. Conclude that the dominant factor is the addition of electron shells, which leads to an increase in atomic radius as you move down a group in the periodic table.