The P atom needs five orbitals to form the five P-Cl bonds. It has a 3s and three 3p orbitals, so it must use one of its 3d orbitals to form the fifth bond. These orbitals are hybridized to form five sp3d orbitals and thus form a trigonal bipyramid. PCl5, there are five P–Cl bonds (thus five pairs of valence electrons around the phosphorus atom) directed toward the corners of a trigonal bipyramid.
- Three hybrid orbitals are directed towards the corners of an equilateral triangle are called equatorial hybrid orbitals. These are planar and bond angle is 1200.
- Two hybrid orbitals are perpendicular to the plane of equatorial hybrid orbital . These are called axial hybrid orbital. They make an angle of 900 with equatorial hybrid orbitals.