Ion–ion Coulomb interaction (Born-style) (Attraction energy scales as −(charge product)/distance (vacuum proportionality))

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Attraction energy scales as −(charge product)/distance (vacuum proportionality)

What each symbol means

SymbolWhat it stands for
rCenter-to-center distance between ions
z_+ z_-Charge product (opposite signs → attractive interaction)

When to use this

Explains magnitude trends alongside lattice models; qualitative for JEE.