1. Molecular Geometry ( Textbook: page383-392)
Valence Electron Pair Repulsion

2. The arrangement of atoms within a given molecule.
Molecular Geometry
The arrangement of atoms within a given molecule.

3. VSEPR Theory
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

4. Molecular Geometry Linear Formula= AX2 Trigonal Planar Formula = AX3
V-shaped Formula = : AX2
Tetrahedral Formula = AX4
Trigonal Pyramidal Formula = : AX3
Trigonal Bipyramidal Formula = AX5
. .
T-shaped Formula = : A X3
See Saw Formula = : AX4
Octahedral Formula = AX6
Note: A –represents the central atom
X – represents the attached atom

5. 2 Bonding pairs 0 lone pairs
( AX2)
Linear
2 Bonding pairs
0 lone pairs

6. Ex: BeCl2
Cl– Be—Cl
1800
Linear
Ex: CO2
O=C=O

7. 3 Bonding Pairs 0 lone pairs
Trigonal Planar
AX3
3 Bonding Pairs
0 lone pairs

8. Ex:BCl3 Cl B
Cl Cl
Trigonal Planar

9. 2 Bonding pairs 2 lone pairs
: AX2
V-shaped
2 Bonding pairs
2 lone pairs

10. Ex: H20
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)

11. 4 bonding pairs 0 lone pairs
Tetrahedral ( AX4)
4 bonding pairs
0 lone pairs

12. Ex: CH4
H 109
H C H H
Ex: SO42- O
O S O

13. Trigonal Pyramidal :AX3
3 bonding pairs
One lone pair

14. Ex: NH3
109.50 N
H H H

15. Exercises
Write the Lewis structure and predict the molecular geometry of the following using VSPER Model
OF2
2) PF3
3) CS2
NSF
SF4
SO42-
PH3
8) SO3