[1] In an ideal trigonal planar species, all three ligands are identical and all bond angles are 120°.

Molecules where the three ligands are not identical, such as H2CO, deviate from this idealized geometry.

Examples of molecules with trigonal planar geometry include boron trifluoride (BF3), formaldehyde (H2CO), phosgene (COCl2), and sulfur trioxide (SO3).

Some ions with trigonal planar geometry include nitrate (NO−3), carbonate (CO2−3), and guanidinium (C(NH2)+3).

[2][3] Nitrogen inversion is the distortion of pyramidal amines through a transition state that is trigonal planar.