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Atomic Radius Trend

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State

Atomic radius decreases across a period as rising Zeff pulls electrons inward, and increases down a group as added shells outweigh it.

Show

Across a period, added protons raise Zeff faster than shielding, drawing outermost electrons closer to the nucleus.

Watch for

Atomic radius does not track atomic number alone — within a period, more protons shrink the atom rather than expand it.