1. Lecture 11 - VSEPR Theory, Molecular Shape 5 Base e - pair geometries will predict 13 Molecular geometries STEPS FOR SUCCESS: 1.draw Lewis 2. bonding pairs 3.lone pairs 4.multiple bonds count as one bonded pair

2. Resonance Structures e.g. O 3 (ozone) OOO.. : :

3. e.g. SO 3 OOOSOSOSOOOOOOOSOSOSOOOO

4. e.g. carbonate ion, CO 3 -2 OOOCOCOCOOOOOOOCOCOCOOOO -2

5. Molecules that don’t obey rules Case 2. Incomplete octets FBFFFBFF     H - Cl  

6. Molecules that don’t obey rules Case 3. Expanded Octets e.g. Phosphorus[Ne] 3s 2 3p 3 e.g. Sulfur[Ne] 3s 2 3p 4 e.gXenon[Ne] 3s 2 3p 6 3d sublevel is close in energy to 3p!

7. Molecules that don’t obey rules Case 3. Expanded Octets ClF ClFF ClPS ClFF ClF 10 electrons! 12 electrons!

8. Molecules that don’t obey rules Case 3. Expanded Octets Xe F F F F : : 12 electrons!

9. Predicting Molecular Shapes VSEPR Theory (Valence Shell Electron Pair Repulsion) - Electron clouds repel one another - Terminal atoms move as far apart as possible - Distinctive geometry results

10. VSEPR Step 1. - count the number of total electron pairs around the central atom - count # Bonding Pairs -count # Nonbonding or Lone Pairs Step 2. Predict the shape!

11. VSEPR ElectronBonds Lone NotationShape Pairs 2 2 0 AX 2 linear 3 3 0 AX 3 trigonal planar 3 2 1 AX 2 Ebent

12. AX 2 e.g. CO 2 (Linear) O = C = O bond angle = 180 o

13. AX 3 e.g. BF 3 (trigonal planar) bond angle = 120 o B F F F

14. AX 2 E e.g. SO 2 (bent) bond angle = 105 o S O O :

15. VSEPR ElectronBonds Lone NotationShape Pairs 4 4 0 AX 4 tetrahedral 4 3 1 AX 3 E trigonal pyramidal 4 2 2 AX 2 E 2 bent

16. AX 4 e.g. methane C     All angles 109.5 o (tetrahedral)

17.     AX 3 E e.g. ammonia.. 107 o (trigonal pyramidal)

18. AX 2 E 2 e.g. water   .. 105 o (bent)

19. VSEPR ElectronBonds Lone NotationShape Pairs 5 5 0 AX 5 trigonal bipyramidal 5 4 1 AX 4 E see-saw 5 3 2 AX 3 E 2 T-shaped 5 2 3 AX 2 E 3 Linear

20. AX 5 Cl ClP Cl ideal angles: 90 o, 120 o (trigonal bipyramidal)

21. AX 4 E FFSFFFFSFF : ideal angles: 90 o, 120 o (seesaw)

22. AX 3 E 2 Cl Cl I Cl : : ideal angles: 90 o (t-shaped)

23. AX 2 E 3 F Xe: F : : angle: 180 o (linear)

24. VSEPR ElectronBonds Lone NotationShape Pairss Pairs 6 6 0 AX 6 octahedral 6 5 1 AX 5 E square pyramidal 6 4 2 AX 4 E 2 square planar

25. AX 6 FFFSFFFFFFSFFFFF all angles 90 o (octahedral)

26. AX 5 E FFFIFF:FFFIFF:FF all angles 90 o (square pyramidal)

27. AX 4 E 2 :F XeF : all angles 90 o (square planar)