Chemistry / Unit 5 Chem 0878 short lesson, about 20 seconds
Atomic Radius Trend
Captions available
The idea
Atomic radius decreases across a period as rising Zeff pulls electrons inward, and increases down a group as added shells outweigh it.
In practice
Across a period, added protons raise Zeff faster than shielding, drawing outermost electrons closer to the nucleus.
Where people slip
Atomic radius does not track atomic number alone — within a period, more protons shrink the atom rather than expand it.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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