Tetrahedral Electron Geometries (AX4, AX3E and AX2E2)
Molecules in this category may have three, four or five atoms.
The configuration is specified as AX4 for the case with five
total atoms and AX3E for the case with four atoms and AX2E3
for the case with three. Remember "E" represents electron
group(s) not involved in bonding, "X" atoms around the central atom
and "A" is the central atom. Molecules of the type AX4
are described as having a tetrahedral,
molecular geometry, those of type AX3E as trigonal pyramidal
molecular geometry, and those of the type AX2E2 as bent molecular geometry.
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Example AX4 Molecules (tetrahedral)
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Example AX3E Molecules (trigonal pyramidal)
Note how loan pairs repel bonds decreasing the bond angle to < 109.5°.
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Example AX2E2 Molecules (bent)
Note how loan pairs repel bonds decreasing the bond angle to < 109.5°.
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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