What is the molecular geometry of the nitrite ion, NO₂⁻, whose central nitrogen carries one lone pair?

Core Concept

Nitrogen owns three electron domains: two N-O bonds averaged by resonance plus one lone pair. Three domains arrange trigonal planar, but the invisible lone pair displaces a corner, leaving the two oxygens angled toward each other. Lone-pair compression trims the O-N-O angle below the ideal 120 degrees to roughly 115.