In
chemistry,
trigonal planar is a
molecular geometry model with one atom at the center and three atoms at the corners of a triangle, called peripheral atoms, all in one plane. In an ideal trigonal planar species, all three ligands are identical and all bond angles are 120° . Such species belong to the
point group D3h. 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 (BF
3),
formaldehyde (H
2CO),
phosgene (COCl
2), and
sulfur trioxide (SO
3). Some ions with trigonal planar geometry include
nitrate (NO
3-),
carbonate ion (CO
32-), and
guanidinium C(NH
2)
3+. In organic chemistry, planar, three-connected carbon centers that are trigonal planar are often described as having
sp2 hybridization.