Molecular Geometry and 3D Structures of Molecules

1. Molecular Geometry and 3D Structures of Molecules

2. Methane Lewis Dot Structure

3. Sites on an atom • A site is something that takes up space around the atom. • Attached atoms • Unshared pairs of electrons • Total sites = attached atoms + unshared pairs

4. Carbon is central atom 4 atoms (H) attached no unshared pairs sites = 4 + 0 = 4 4 sites Sites in Methane

5. VSEPR Theory • Electrons repel • Will move as far apart as possible in 3 dimensions • Actually electron clouds that repel. • Attached atoms positioned by repulsion of electrons clouds bonded to.

6. Methane Summary • clouds arrange tetrahedrally • clouds 109.5o apart • Shape is tetrahedral

7. Methane ball and stick

8. Wedge is coming out of plane of paper dash behind compare to ball and stick 3D representation of methane

9. Comparison of Methane Structures

10. Space filling model of methane

11. Summary sheet

12. Ammonia Lewis Dot Structure

13. 3 attached atoms 1 unshared pair total of 4 sites Clouds tetrahedral Sites in Ammonia

14. Ammonia Ball and Stick

15. Clouds still tetrahedral one cloud has unshared pair invisible cloud repels more strongly than bonds pushes bonds together bond angle 107.7 trigonal pyramidal 3D Representation of Ammonia

16. Comparison of Ammonia Structures

17. Ammonia space fill

18. Summary sheet

19. Water Lewis Dot Structure

20. 2 attached atoms 2 unshared pairs 4 sites Clouds tetrahedral Sites in Water

21. Water Ball and Stick

22. Clouds still tetrahedral two clouds have unshared pairs invisible clouds repel more strongly than bonds push bonds together bond angle 105 bent 3D Representation of Water

23. Comparison of Water Structures

24. Water Space Fill

25. Summary sheet

26. HCl Lewis Dot Structure

27. 1 attached atom 3 unshared pairs 4 sites Clouds tetrahedral Sites in HCl

28. HCl Ball and Stick

29. Clouds still tetrahedral three clouds have unshared pairs invisible clouds bond angle 180 linear 3D Representation of HCl

30. Comparison of HCl Structures

31. HCl Space Fill

32. Summary sheet

33. CH2O Lewis Dot Structure

34. 3 attached atoms 0 unshared pairs 3 sites Clouds trigonal planar Sites in CH2O

35. CH2O Ball and Stick

36. clouds go to corners of equilateral triangle bond angle 120 trigonal planar 3D Representation of CH2O

37. Comparison of CH2O Structures Since planar, both structures are the same.

38. CH2O Space Fill

39. Summary sheet

40. SO2 Lewis Dot Structure

41. 2 attached atoms 1 unshared pairs 3 sites Clouds trigonal planar Sites in SO2

42. SO2 Ball and Stick

43. Clouds go to corners of equilateral triangle unshared pair is invisible cloud bond angle between 105 and 120 bent 3D Representation of SO2

44. Comparison of SO2 Structures Since bent, both structures are the same.

45. SO2 Space Fill

46. Summary sheet

47. SO2 Lewis Dot Structure…Double bonded oxygen

48. 1 attached atoms 2 unshared pairs 3 sites Clouds trigonal planar Sites on O in SO2

49. Clouds go to corners of equilateral triangle unshared pairs are invisible clouds bond angle 180 linear around double bound oxygen 3D Representation of SO2

50. Comparison of SO2 Structures Linear around double bonded O