Which of the following best describes the trend in atomic radius as you move down a group on the periodic table, and what is the primary cause of this trend?

• A. Atomic radius increases because electrons are removed from the atom.
• B. Atomic radius decreases because nuclear charge increases.
• C. Atomic radius increases due to the addition of electron shells.
• D. Atomic radius remains constant because shielding effect balances nuclear charge.

Answer: (C)

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 moving down a group in the periodic table means moving to elements with higher principal quantum numbers (n), which corresponds to adding more electron shells or energy levels.
3. Recall that each additional electron shell increases the distance between the nucleus and the outermost electrons, which tends to increase the atomic radius.
4. Consider the shielding effect, where inner electrons partially block the attraction between the nucleus and outer electrons, reducing the effective nuclear charge felt by the outermost electrons.
5. Conclude that the primary cause of the increase in atomic radius down a group is the addition of electron shells, which outweighs the increase in nuclear charge due to shielding.