easy · MCAT chem-phys

Why does the atomic radius of elements generally increase as you move from top to bottom within a group on the periodic table?

1. The nucleus becomes progressively less dense down the group, exerting a much weaker gravitational pull on the surrounding electron cloud.
2. The effective nuclear charge increases so significantly down the group that it paradoxically pushes the valence electrons farther outward.
3. Electron-electron repulsion within the valence shell decreases steadily down a group, letting the atom expand outward.
4. The addition of new principal energy levels (shells) increases the distance between the nucleus and the outermost electrons.

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