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 D_3h. 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 (NO₃^-), carbonate ion (CO₃^2-), and guanidinium C(NH₂)₃⁺. In organic chemistry, planar, three-connected carbon centers that are trigonal planar are often described as having sp² hybridization.