Trigonal pyramid (chemistry)

In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. When all three atoms at the corners are identical, the molecule belongs to point group C_3v. Some molecules and ions with trigonal pyramidal geometry are ammonia (NH₃), xenon trioxide, XeO₃, the chlorate ion, ClO₃^-, and the sulfite ion, SO₃^2-. In organic chemistry, molecules which have a trigonal pyramidal geometry are sometimes described as sp³ hybridized. The AXE method for VSEPR theory states that the classification is AX₃E₁.