1. Chapter 6 – 3 Molecular Geometry (p. 214 – 218)

2. VSEPR: stands for... Valence Shell Electron Pair Repulsion
Predicts three dimensional geometry of molecules.
Valence shell electrons - outermost electrons.
Electron Pair repulsion - electron pairs try to get as far away as possible in order to minimize repulsive forces.
Can determine the angles of bonds.

3. Lone pairs repel more strongly than bonding pairs!!!
VSEPR
Based on the number of pairs of valence electrons, both bonding and nonbonding (lone pairs) around the central atom.
Lone pairs repel more strongly than bonding pairs!!!

4. VSEPR
Lone pairs reduce the bond angle between atoms.
Bond Angle

5. Using the VSEPR Model 1. Draw the electron-dot structure
2. Identify the central atom
3. Predict the shape of the molecule using the # of bonding pairs and lone pairs around the central atom.
double/triple bonds = ONE bonding pair

6. CO2
O C O
2 bonding pairs
0 lone pair
LINEAR
180°

7. 3 bonding pairs, 0 lone pair
The farthest the electron pairs can get away is 120º.
Shape is flat and called trigonal planar. H
120º H C C O H O H

8. H H C H H VSEPR 4 bonding pairs 0 lone pair.
There are 4 pairs of electrons pushing away.
The furthest the electron pairs can get away is 109.5º H H C H H

9. 4 bonding pairs
0 lone pair
CH4
TETRAHEDRAL
109.5°

10. 4 bonding pairs, 0 lone pair
A pyramid with a triangular base. H
109.5º C
CH4 H H H

11. 3 bonding pairs, 1 lone pair
Shape is called trigonal pyramidal. N H N H H H
<109.5º H H

12. F P F F
PF3
3 bonding pairs
1 lone pair
TRIGONAL PYRAMIDAL

13. 2 bonding pairs, 2 lone pairs
Shape is called bent. O H O H
<109.5º H H

14. 2 bond
2 lone
H2O
BENT

15. 2 bonding pairs
0 lone pair
LINEAR
180°
BeH2

16. 3 bonding pairs
0 lone pair
BF3
TRIGONAL PLANAR
120°

17. 2 bonding pairs
1 lone pair
SO2
BENT
<120°

18. 5 bonding pairs
0 lone pair
PCl5
TRIGONAL BIPYRAMIDAL
120°/90°

19. 6 bonding pairs
0 lone pair
SF6
OCTAHEDRAL
90°

20. Learning Check
Determine the molecular geometry of each of the following:
A. CCl4
tetrahedral
B. SO3
trigonal planar
C. PCl3
trigonal pyramidal

21. Which molecule is polar?HF
NH3
CCl4