Skip to content
CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Lone pair

A pair of valence electrons that belongs to one atom and is not shared in a bond. It counts toward that atom's octet only, and on a central atom it takes up space and shapes the molecule.

HOH
O in HX2O\ce{H2O} has two lone pairs and two bonding pairs.

Example

NHX3\ce{NH3} has one lone pair on N, which makes it trigonal pyramidal and lets it bond to HX+\ce{H+} to form NHX4X+\ce{NH4+}.

See alsoBonding pairLewis baseElectron domainFormal charge