9.2 VSEPR theory of atoms lone bonded to pairs on Arrangement of Molecular Class central atom central atom electron pairs Geometry AB5 5 0 trigonal trigonal bipyramidal bipyramidal Phosphorus Pentachloride (PCL) 90 B 90° 120° Trigonal bipyramidalClass # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry AB5 5 0 trigonal bipyramidal trigonal bipyramidal Phosphorus Pentachloride (PCl ) 9.2 VSEPR theory (PCl5)