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CHEM 121 Studioby Learn4Less · UBC CHEM 121

CHEM 121 glossary

Trigonal planar

Three domains around a central atom, all in one plane and pointing to the corners of an equilateral triangle, 120° apart. It is both the electron-domain geometry for SN = 3 and the molecular shape of AX3\mathrm{AX_3}.

Central B atom bonded to 3 F atoms, with no lone pairs.BFFF120°Ideal bond angle: 120°
BFX3\ce{BF3}: three F atoms 120° apart in a plane.

Example

COX3X2−\ce{CO3^2-} and NOX3X−\ce{NO3-} are trigonal planar with all O–X–O angles 120°; SOX2\ce{SO2} has a trigonal planar electron geometry but is bent.

See alsoBentSteric numberElectron-domain geometry