1. Chapter 9 Chemical Bonding Theories Valence Bond Theory: Uses Lewis Structures Bonds form using shared electrons between overlapping orbitals on adjacent atoms. Orbitals arrange around central atom to avoid each other. Two types of bonds: sigma and pi. Molecular Orbital Theory: Uses MO Diagrams Orbitals on atoms “mix” to make molecular orbtials, which go over 2 or more atoms. Two electrons can be in an orbital. Orbitals are either: bonding, antibonding, or nonbonding. Bonds are either: sigma or pi.

2. Orbitals on bonding atoms overlap directly between bonding atoms Sigma (  ) Bonding Between s orbitals Between p orbitals

3. Consider VSEPR Shapes and bonding: Sigma (s) Bonding

4. What’s wrong with this picture? Atoms bond by having their valence orbitals overlap

5. Enter question text... 1.1 2.2 3.3

6. Orbitals don’t go in same directions as atomic orbitals. 2s 2p z 2p x 2p y Orbitals in CH 4 Orbitals on C

7. Orbitals don’t go in same directions as atomic orbitals. 2s 2p z 2p x 2p y Orbitals in CH 4 Conclusion: Atomic orbitals change shape when they make molecules.

8. Hybrid Orbitals Atomic valence orbitals “combine and mix” to form new “Hybrid Orbitals” Hybrid orbitals go in the VSEPR electron geometry directions.

9. Types of Hybrid Orbitals

10. Types of Hybrid Orbitals: 2 Pairs

11. Types of Hybrid Orbitals: 3 Pairs

12. Types of Hybrid Orbitals: 4 Pairs

14. Hybrid orbitals in H 2 O? 1.sp 2.sp 2 3.sp 3 4.sp 3 d 5.sp 3 d 2

15. Hybrid orbitals in O 3 ? 1.sp 2.sp 2 3.sp 3 4.sp 3 d 5.sp 3 d 2

16. Hybrid orbitals in CO 2 ? 1.sp 2.sp 2 3.sp 3 4.sp 3 d 5.sp 3 d 2

17. Hybrid orbitals in SF 4 ? 1.sp 2.sp 2 3.sp 3 4.sp 3 d 5.sp 3 d 2

18. Hybrid orbitals used for sigma bonds and lone pairs. Unhybridized p orbitals used for pi bonds, or they are empty.

19. Sigma Bonding Orbitals overlap directly between two nuclei:

20. NH 3

21. CH 2 O

22. Sigma Bonding involves hybrid orbitals and/or H 1s orbitals. Pi bonding involves unhybridized p orbitals. Sigma vs. Pi Bonding

23. Pi Bond Formation

24. Bonding in Ethene

25. Bonding in Acetylene

26. Bonding in Formaldehyde

27. How many bonds in acetonitrile? 1.7 sigma, 0 pi 2.6 sigma, 1 pi 3.5 sigma, 2 pi 4.4 sigma, 3 pi

28. Bonding in Benzene

29. Advanced: Allene Each end carbon is a flat trigonal. Are they co-planar or perpendicular?

30. Bonding in Allene

31. Conformations vs. Isomers Isomers: Molecules with same formula but different structure Conformers: Different temporary shapes of the same molecule

32. Bond Rotations CAN happen around single bonds Cannot happen around double bonds Examples: dichloroethane and diclhloroethene

33. Types of Isomers Constitutional: Different bond connections Geometric/Stereoisomers: Same connections, different directions

34. Cis-Trans Stereoisomerization When two groups are on a “side” of a molecule. cis trans

35. Can these molecules have cis-trans isomers?

36. What are these? 1.Constitutional isomers 2.Stereoisomers 3.Conformations 4.None of these

37. What are these? 1.Constitutional isomers 2.Stereoisomers 3.Conformations 4.None of these

38. What are these? 1.Constitutional isomers 2.Stereoisomers 3.Conformations 4.None of these

39. A message from Mom.