Molecular Geometry 118 Opener Draw the lewis dot

Molecular Geometry 11/8 Opener: Draw the lewis dot configuration for water (H 2 O). 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= AX 2 Trigonal Planar Formula = AX 3 Bent (tetrahedral) Formula = : AX 2 Tetrahedral Formula = AX 4 Trigonal Pyramidal Formula = : AX 3 Trigonal Bipyramidal Formula = AX 5. . T-shaped Formula = : A X 3 See Saw Formula = : AX 4 Octahedral Formula = AX 6 Note: A –represents the central atom X – represents the attached atom

Linear( AX 2) 2 Bonding pairs 0 lone pairs

Ex: Be. Cl 2 Cl– Be—Cl 1800 Linear Ex: CO 2 O=C=O 1800

Trigonal Planar AX 3 3 Bonding Pairs 0 lone pairs

Ex: BCl 3 Cl B 120 Cl Cl Trigonal Planar

Bent: AX 2 2 Bonding pairs 2 lone pairs

Ex: H 20 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)

Tetrahedral ( AX 4) 4 bonding pairs 0 lone pairs

Ex: CH 4 H 109 H C H H Ex: SO 42 O O S O O

Trigonal Pyramidal : AX 3 3 bonding pairs One lone pair

Ex: NH 3 109. 50 N H H H

Exercises Write the Lewis structure and predict the molecular geometry of the following using VSPER Model 1) OF 2 2) PF 3 3) CS 2 4) NSF 5) SF 4 6) SO 427) PH 3 8) SO 3