When the central atom is surrounded by three things, it has a trigonal
planar geometry, with 120o angles between the bonds.
| Type | Bond Angle | Example | Lewis Structure |
| AX3: Trigonal Planar | 120o | AlH3 |  |
If one of the bonded atoms is replaced by a lone pair, the molecule assumes a
bent geometry, with a 120o angle between the bonds.
| Type | Bond Angle | Example | Lewis Structure |
| AX2E: Bent | 120o | SO2 |  |
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