1. Chapter 3 Simple Bonding Theory
Lewis Dot Structures
Resonance
Formal Charge
VSEPR: the subtle effects

2. Lewis Dot Structures 1. Count valence electrons 2. Arrange atoms
3. Add bonds
4. Add lone pairs
5. Convert lone pairs to bonding pairs (octet rule and exceptions)

3. Lewis Dot Structures
Examples: CO2 SO3 N2O XeF4 ClF3 PCl6–

4. Why does the octet rule work?

5. More complex
NO2 NO

6. = Group # - #unshared electrons on atom - # bonds to atom
Formal Charge
= Group # - #unshared electrons on atom - # bonds to atom
Example: O3

7. Resonance
Example: SO3

8. Resonance and Formal Charge
Example: SCN-

9. Resonance and Formal Charge
Example: SCN-

10. Octet Rule vs. Pi Bonding Trends
BeF2 and
BF3

11. Octet Rule vs. Formal Charge
Always follow octet rule Exceptions? SO42-

12. VSEPR Maximize “personal space” CO2, SO3, SO42–, PCl5, SF6
Lone pairs vs. bonding pairs?
Single bonds vs. multiple bonds?
Electronegativity effects

13. VSEPR

14. Lone Pair Effects

15. Pi Bonds vs. Lone Pairs: Guess these bond angles.

16. Pi Bonds vs. Lone Pairs: Guess these bond angles.

17. Pi Bonds vs. Lone Pairs

18. Pi Bonds vs. Lone Pairs
Which take up more room: lone pairs or a pi bond?

19. Electronegativity Effects

20. Electronegativity Effects
Molecule X-P-X Angle o PF
PCl
PBr
Explain this trend.

22. Electronegativity Effects
Molecule X-P-X Angle o PF
PCl
PBr
Terminal Atom Effects:
F: Electron density of the bond pairs is mostly near the F.
Electron density near the central atom is less, which
decreases bond pair – bond pair repulsion near the P.

24. Electronegativity Effects
Molecule H-X-H Angle o
H2O
H2S
H2Se
Explain this trend.

26. Electronegativity Effects
Molecule H-X-H Angle o
H2O
H2S
H2Se
Explain this trend.
Central atom effects:
O: as O pulls more electron density toward it, bonds have
more electron density near the central atom. This causes
greater bond pair – bond pair repulsions.

27. Electronegativity Effects
Molecule X-As-X Angle o
AsF3
AsCl3
AsBr3
Predict this trend.

28. Predicting Positions of Different Atoms
PF3Cl Are Cl atoms axial or equatorial?

29. Homework Chapter 3
7, 9 acde, 11, 12,14,29,30a