1. Chapter 13 Molecular Shapes VSEPR Theory

2. Molecular Shape Molecular shape or molecular geometry is the three-dimensional arrangement of the atoms in a molecule.

3. Molecular Shape Molecular shape determines several properties of a substance including: –reactivity –polarity –phase of matter –color –magnetism –biological activity

4. Olfaction – sense of smell Lock-and-Key Theory: humans can smell various odors because each three- dimensional odor molecule fits into only one type of receptor.

6. Gustation – the sense of taste Taste receptors are located on the tongue and are sensitive to four major tastes: salty, sweet, sour and bitter. Taste receptors respond differentially to the varying shapes of food and liquid molecules.

7. H2H2 HH 2(1) = 2e - Any 2 atoms linear

8. What about molecules consisting of more than two atoms For this we must use the VSEPR Theory

9. VSEPR Theory Valence Shell Electron Pair Repulsion Theory Predicts the molecular shape of a bonded molecule containing a central atom(s). Electrons around the central atom arrange themselves as far apart from each other as possible So only electrons (lone pairs or bonds) connected to the central atom are important.

10. Five Molecular Shapes See the table in your notes

12. Steps in Determining Molecular Shape 1.Draw the Lewis Structure for the Molecule. 2.Count the number of atoms attached to the central atom. 3.Count the number of lone pairs attached to the central atom. 4.Use your counts on steps 2 and 3 to determine the shape of the molecule.

14. H2SH2S Dihydrogen monosulfide is commonly known as sewer gas. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs. HHS 2(1)+6 = 8e - 2/2 angular

15. H2SH2S Dihydrogen monosulfide is commonly known as sewer gas. This colorless, toxic and flammable gas is responsible for the foul odor of rotten eggs. HH S

16. Methane (CH 4 ) 4 + 4(1) = 8e -

17. Methane (CH 4 ) 4 + 4(1) = 8e - 4 atoms attached to the central atom. 0 lone pairs on the central atom. 4/0 Tetrahedral shape

18. Methane (CH 4 ) 4 + 4(1) = 8e - 4 atoms attached to the central atom. 0 lone pairs on the central atom. 4/0 Tetrahedral shape

19. HCN HNC 1+4+5 = 10e -

20. HCN HNC 1+4+5 = 10e -

21. HCN HNC 1+4+5 = 10e -

22. HCN HNC 1+4+5 = 10e -

23. HCN HNC 1+4+5 = 10e -

24. HCN HNC 1+4+5 = 10e - 2/0 linear

25. H2SH2S H H S 2/2 angular

26. SO 2 OOS 6+2(6) = 18e -

27. SO 2 OOS 6+2(6) = 18e -

28. SO 2 OOS 6+2(6) = 18e - 2/1 angular

29. CH 4 4/0 tetrahedral

30. NO 3 - OON 5+3(6)+1 = 24e - O

31. NO 3 - OON 5+3(6)+1 = 24e - O

32. NO 3 - OON 5+3(6)+1 = 24e - O

33. NO 3 - OON 5+3(6)+1 = 24e - O 3/0 trigonal planer [ ] -

34. SOCl 2

36. Draw the Lewis structure for an acetate ion?

38. What’s the shape of acetate? 4/0 tetrahedral 3/0 trigonal planer

39. Homework  Worksheet Chapter 13.  Study Guide Chapters 12 – 14 (due by the end of the week).