trigonal bipyramidal (trigonal bipyramidal shape; trigonal bipyramidal geometry)

A molecular shape that results when there are five bonds and no lone pairs on the central atom in the molecule. Three of the bonds are arranged along the atom's equator, with 120° angles between them; the other two are placed at the atom's axis. Axial bonds are at right angles to the equatorial bonds. The PCl5 molecule has a trigonal bipyramidal molecular geometry.