Trigonal Planar Electron Geometries (AX3 and AX2E)
Molecules in this category may have three or four atoms. The
configuration is specified as AX3 for the case with four
total atoms and AX2E for the case with only three
atoms. The "E" represents the electron group that is not involved
in bonding. Molecules of the type AX3 are described
as having a trigonal
planar molecular geometry and molecules of the type AX2E are
described as having a bent molecular geometry.
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Example AX3 Molecules (trigonal planar)
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Example AX2E Molecules (bent)
Note how loan pairs repel bonds decreasing the bond angle to < 120°.
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Reference and Technical Info
* Measured geometry (from spectroscopic measurements) sourced from:
The NIST Computational Chemistry Comparison and Benchmark Database
NIST Standard Reference Database Number 101
Release 22, May 2022, Editor: Russell D. Johnson III
https://cccbdb.nist.gov/
Other geometries are based on estimates from quantum computations.
Last Update: July 25, 2026
Expires: --
J. Gutow
Expires: --
J. Gutow