Atomic Radius Trends (Covalent/metallic radii decrease across a period, increase down a group)

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Covalent/metallic radii decrease across a period, increase down a group

What each symbol means

SymbolWhat it stands for
rAtomic radius (covalent or metallic depending on context)

When to use this

Trends assume comparable definitions. Transition metals show smaller left-to-right changes due to d shielding. Noble gases use van der Waals radii — not comparable to covalent radii in strict ranking questions.