Atomic Size Trends

Down a group: Radius increases (more electron shells).
Across a period: Radius decreases (more protons pulling electrons closer).
Cations: Smaller than parent atom (fewer electrons, same nuclear charge).
Anions: Larger than parent atom (more electrons, same nuclear charge).
Isoelectronic series: Same number of electrons — more protons = smaller radius.

Atomic & Ionic Size Comparison

Compare atoms and ions by relative size. Click the larger species or rank them smallest to largest.

Streak: 0 Best: 0

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