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

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

3. VSEPR Theory Based on Electron Dot (Lewis structures)
06/10/99
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

4. VSEPR overview Names of Shapes: tetrahedral trigonal pyramidal Bent
06/10/99
Each shape has a name
(you will have to know these)
Names of Shapes:
tetrahedral
trigonal pyramidal
Bent
Linear
trigonal planar

5. Models
Tetrahedral
Triangular Planar
Bent or V
Linear
Trigonal pyramidal

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

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

8. .. ..
water, H2O
109.5° (109.5°)
109.5° (107°)
109.5° (104.5°)

9. .. ..

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

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

12. 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

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