VSEPR theory predicts molecular shapes based on electron pair repulsion around a central atom. It assumes that the molecular structure forms in a way to minimize repulsion between bonding and non-bonding electron pairs. The theory names molecular shapes such as tetrahedral, trigonal pyramidal, bent, linear, and trigonal planar based on the number of electron pairs around the central atom. Examples are given of the Lewis structures and predicted shapes of methane, ammonia, water, carbon dioxide, beryllium chloride, and boron trifluoride.

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VESPER THEORY
Presented By: Sagar Panhwar

3. VValencealence
SShellhell
EElectronlectron
PPairair
RRepulsionepulsion
TheoryTheory
Planar
triangular
Tetrahedral
Trigonal
pyramidal
Bent

4. VSEPR theory assumes that the shape of aVSEPR theory assumes that the shape of a
molecule is determined by themolecule is determined by the repulsionrepulsion ofof
electron pairs.electron pairs.
Molecular ShapeMolecular Shape

5. VSEPRVSEPR TheoryTheory
• 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

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

7. Triangular PlanarTetrahedral
Trigonal pyramidal
Linear
Bent or V
Models

8. methane, CHmethane, CH44
Bonds are all evenly spaced electronsBonds are all evenly spaced electrons
109.5°109.5°
TetrahedralTetrahedral

9. Less repulsion between the bonding pairs of electronsLess repulsion between the bonding pairs of electrons
.. ammoniaammonia
NHNH33
..
..
..
TrigonalTrigonal
PyramidalPyramidal

10. .. ..
..
109.5° (109.5° (109.5109.5°)°) 109.5° (109.5° (107107°)°) 109.5° (109.5° (104.5°)104.5°)
water, Hwater, H22OO

11. .. ..
..

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

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

14. Molecule Lewis Structure Number of
electron pairs
H2
O
CO2
SHAPE
Bent or V
4
(2 shared
2 lone pairs)
2
Linear

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