Which statement best describes the general trend in atomic radius for elements within the same group of the periodic table?

• A. Atomic radius increases as you move down a group.
• B. Atomic radius first increases and then decreases as you move down a group.
• C. Atomic radius remains constant as you move down a group.
• D. Atomic radius decreases as you move down a group.

Answer: (A)

Verified step by step guidance

1. Understand that the 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 within a group (column) of the periodic table, elements have the same number of valence electrons but differ in the number of electron shells (energy levels).
3. Recognize that as you move down a group, each successive element has an additional electron shell compared to the one above it, which increases the distance between the nucleus and the outermost electrons.
4. Consider the effect of increased electron shells: even though the nuclear charge increases, the inner shells shield the outer electrons from the full positive charge of the nucleus, reducing the effective nuclear attraction on the outermost electrons.
5. Conclude that because of the added shells and shielding effect, the atomic radius increases as you move down a group in the periodic table.