Valence Shell Electron Pair Repulsion Theory Planar triangular Valence Shell Electron Pair Repulsion Theory 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 Names of Shapes: tetrahedral trigonal pyramidal Bent 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 Bent or V Linear Trigonal pyramidal

methane, CH4 Tetrahedral 109.5° Bonds are all evenly spaced electrons

ammonia NH3 .. .. .. .. Trigonal Pyramidal Less repulsion between the bonding pairs of electrons

.. .. water, H2O 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

Number of electron pairs SHAPE Molecule Lewis Structure Number of electron pairs CH4 NH3 4 Tetrahedral Trigonal Pyramidal 4 (3 shared 1 lone pair)

Number of electron pairs Molecule Lewis Structure Number of electron pairs H2O SHAPE Bent or V 4 (2 shared 2 lone pairs) Linear CO2 2

Number of electron pairs SHAPE Molecule Lewis Structure Number of electron pairs BeCl2 BF3 Linear 2 Trigonal Planar 3