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 C3v. Some molecules and ions with trigonal pyramidal geometry are
ammonia (NH
3),
xenon trioxide, XeO
3, the
chlorate ion, ClO
3-, and the
sulfite ion, SO
32-. 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 AX
3E
1.