Name:                               Date:                         Class Notes
            Chemistry
                                   VSEPRTheory
                  There are twotheories that describe covalent bonding. The valence shell electron pair repulsion
            (VSEPR)theoryandthevalencebondtheory. TheVSEPRtheoryhelpstoexplainandpredicttheshapesof
            polyatomic ions and molecules but not how the bonds are formed. The valence bond theory explains how
            covalent bonding takes place by the combining of orbitals to create new orbitals with different shapes.
            Together, these twoideas help us understand the bonding, shapes and properties of many molecular
            substances and polyatomicions.
            Note:Ioniccompoundsdonotformmolecules. Ioniccompoundsarecrystallinesolidsrepresentedby
            formula units. A formula unit is the smallest ratio of the elements in an ionic compound,
            VSEPRTheory
                  Thevalenceshell electron pair repulsion theory describes how the molecule or polyatomic ion shape is
            formedbytherepulsionofthebondsandelectronpairs (lonepairs). Rememberbondsandelectron pairsare
            bothmadeofelectronsandallelectronsare negativewhich means bondsandelectronpairswillrepel each
            other. In doing so, the bonds and electron pairs will move as far away from each other as possible to create a
            morestableform,thuscreating twotypes ofgeometry: electronic geometry andmolecular geometry.
                  Theelectronicgeometryistheshapeformedbythearrangementofelectrondenseregionsaround
            acentral atom. Since bonds are electrons this geometry includes both bonds and lone pairs. The molecular
            geometryistheshapeformedonlybythebondsandexcludestheelectronpairs.
                                                                   lone pair
                  Example:         NH                       N
                                       3                H       H
                                                            H
                    electronic geometry              molecular geometry
                                lone pair
                                                                     bonds only
                        tetrahedral                   trigonal pyramidal
            Copyright©2017 by DarrellCausey, Jr.
                                ELECTRONICANDMOLECULARGEOMETRIES
                                     Molecules and polyatomic ions have definite shapes.
                                                AB E                      AB E
                 Trigonal Planar                  2 1                        1 2
                                                Angular                    Linear
                 Tetrahedral                    AB E
                                                   3 1                    AB E                   AB E
                                                                             2 2                    1 3
                                           Trigonal Pyramidal             Angular                 Linear
                 Trigonal Bipyramidal                 AB E
                                                         4 1              AB E                    AB E
                                                                             3 2                     2 3
                                                     Seesaw               T-shaped                Linear
                  Octahedral                           AB E
                                                         5 1                  AB E
                                                                                4 2
                                                  Square Pyramidal          Square Planar
               Copyright©2017 by DarrellCausey, Jr.