Valence Shell Electron Pair Repulsion Theory Planar triangular

Valence Shell Electron Pair Repulsion Theory Planar triangular Tetrahedral Trigonal pyramidal Bent

Molecular Shape VSEPR theory assumes that the shape of a molecule is determined by the repulsion of electron pairs.

VSEPR Theory • Based on Electron Dot (Lewis structures) • Theory predicts shapes of compounds • abbreviated VSEPR • VSEPR (pronounced “vesper”) stands for Valence Shell Electron Pair Repulsion • VSEPR predicts shapes based on electron pairs repelling (in bonds or by themselves) • Electrons around central nucleus repel each other. So, structures have atoms maximally spread out

VSEPR overview • Each shape has a name (you will have to know these) • Names of Shapes: • tetrahedral • trigonal pyramidal • Bent • Linear • trigonal planar

Models Tetrahedral Triangular Planar Trigonal pyramidal Bent or V Linear

methane, CH 4 Tetrahedral 109. 5° Bonds are all evenly spaced electrons

. . . . ammonia NH 3 Trigonal Pyramidal Less repulsion between the bonding pairs of electrons

. . . water, H 2 O 109. 5° (109. 5°) 109. 5° (107°) 109. 5° (104. 5°)

Bent or V 2 unshared pairs of e’s at top of O repel bonds and force them to bend

Molecule CH 4 Lewis Structure Number of electron pairs SHAPE 4 Tetrahedral NH 3 4 Trigonal Pyramidal (3 shared 1 lone pair)

Molecule Lewis Structure Number of electron pairs SHAPE Bent or V H 2 O 4 (2 shared 2 lone pairs) Linear CO 2 2

Molecule Be. Cl 2 BF 3 Lewis Structure Number of electron pairs 2 3 SHAPE Linear Trigonal Planar