Question

How does atomic radius change as you go down a group?


Increases (more electrons, more shells - greater radius)


Decreases (element lower in a group have fewer electrons)

Answer 1

It increases.

As you go down a group (same column) each element has an extra electron shell (higher principal quantum number), so the valence electrons are on average farther from the nucleus. Although nuclear charge (protons) also increases, increased shielding by inner electrons means the effective pull on the outer electrons does not grow enough to overcome the added shell size. So atomic radius gets larger.

(The second option is incorrect — elements lower in a group have more, not fewer, electrons. Note minor exceptions occur in transition series/lanthanide contraction, but the overall trend is increase down the group.)