Molecular Geometry 11/8 Opener: Draw the lewis dot configuration for water (H2O). How many pairs of non bonding electrons does water have?

Molecular Geometry The arrangement of atoms within a given molecule.

VSEPR Theory VSEPR: Valence Shell Electron-Pair Repulsion Is based on simple electrostatic repulsions of electron pairs Assumption  Electrons in chemical bonds( single, double, or triple) and unshared electron pairs are negative centers that repel each other

Molecular Geometry Linear Formula= AX2 Trigonal Planar Formula = AX3 Bent (tetrahedral) Formula = : AX2 Tetrahedral Formula = AX4 Trigonal Pyramidal Formula = : AX3 Trigonal Bipyramidal Formula = AX5 . . T-shaped Formula = : A X3 See Saw Formula = : AX4 Octahedral Formula = AX6 Note: A –represents the central atom X – represents the attached atom

2 Bonding pairs 0 lone pairs Linear( AX2) 2 Bonding pairs 0 lone pairs

Ex: BeCl2 Cl– Be—Cl 1800 Linear Ex: CO2 O=C=O

3 Bonding Pairs 0 lone pairs Trigonal Planar AX3 3 Bonding Pairs 0 lone pairs

Ex:BCl3 Cl B 120 Cl Cl Trigonal Planar

2 Bonding pairs 2 lone pairs Bent: AX2 2 Bonding pairs 2 lone pairs

Ex: H20 H– O –H since lone pair is more electronegative than the bonding pairs it tends to push the bonding pairs closer together, thereby decreasing the angle between them O H H v-shaped (less than 1090)

4 bonding pairs 0 lone pairs Tetrahedral ( AX4) 4 bonding pairs 0 lone pairs

Ex: CH4 H 109 H C H H Ex: SO42- O O S O

Trigonal Pyramidal :AX3 3 bonding pairs One lone pair

Ex: NH3 109.50 N H H H

Exercises Write the Lewis structure and predict the molecular geometry of the following using VSPER Model OF2 2) PF3 3) CS2 NSF SF4 SO42- PH3 8) SO3