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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Electron-domain geometry

The arrangement of all electron domains (bonds and lone pairs) around a central atom, set by the steric number alone. It can differ from the molecular geometry, which ignores lone pairs.

Central N atom bonded to 3 H atoms, with 1 lone pair.HHNH109.5°Ideal bond angle: 109.5°
NHX3\ce{NH3}: tetrahedral electron-domain geometry, but a trigonal pyramidal molecule.

Example

CHX4\ce{CH4}, NHX3\ce{NH3} and HX2O\ce{H2O} all have SN = 4 and a tetrahedral electron-domain geometry, yet their shapes are tetrahedral, trigonal pyramidal and bent.

See alsoMolecular geometrySteric numberElectron domainTetrahedral