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VSEPR Theory

VSEPR Theory. Valence Shell Electron Pair Repulsion. VSEPR THEORY: AT THE CONCLUSION OF OUR TIME TOGETHER, YOU SHOULD BE ABLE TO:. Use VSEPR to predict molecular shape Name the 6 basic shapes that have no unshared pairs of electrons Name a few variations off of these basic shapes.

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VSEPR Theory

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  1. VSEPR Theory Valence Shell Electron Pair Repulsion

  2. VSEPR THEORY:AT THE CONCLUSION OF OUR TIME TOGETHER, YOU SHOULD BE ABLE TO: Use VSEPR to predict molecular shape Name the 6 basic shapes that have no unshared pairs of electrons Name a few variations off of these basic shapes

  3. VSEPR Theory

  4. Redneck Innovations

  5. Molecular Shapes Lewis structures show which atoms are connected where, and by how many bonds, but they don't properly show 3-D shapes of molecules. To find the actual shape of a molecule, first draw the Lewis structure, and then use VSEPR Theory.

  6. Valence Shell Electron-Pair Repulsion Theory or VSEPR Molecular Shape is determined by the repulsions of electron pairs Electron pairs around the central atom stay as far apart as possible. Electron Pair Geometry - based on number of regions of electron density Consider non-bonding (lone pairs) as well as bonding electrons. Unshared repel the most. Electron pairs in single, double and triple bonds are treated as single electron clouds. Molecular Geometry - based on the electron pair geometry, this is the shape of the molecule

  7. Electron-group Repulsions And The Five Basic Molecular Shapes.

  8. LET’S CONSIDER THESE BASIC SHAPES AND SOME VARIATIONS OF THEM…

  9. Linear • 2 atoms attached to central atom • 0 unshared pairs (lone pairs) • Bond angle = 180o • Type: AX2 • Ex. : BeF2

  10. Linear • Carbon dioxide CO2

  11. The Single Molecular Shape Of The Linear Electron-group Arrangement. Examples: CO2, BeF2

  12. Trigonal Planar • Boron Trifluoride BF3

  13. Trigonal Planar • 3 atoms attached to central atom • 0 lone pairs • Bond angle = 120o • Type: AX3 • Ex. : AlF3

  14. Class Shape The Two Molecular Shapes Of The Trigonal Planar Electron-group Arrangement. Examples: H2CO, BCl3, NO3-, CO32-

  15. Effect of Double Bonds 1160 real Factors Affecting Actual Bond Angles Bond angles are consistent with theoretical angles when the atoms attached to the central atom are the same and when all electrons are bonding electrons of the same order. Some exceptions follow: 1200 larger EN 1200 ideal greater electron density

  16. Effect of Nonbonding Pairs Factors Affecting Actual Bond Angles Lone pairs repel bonding pairs more strongly than bonding pairs repel each other 950

  17. Trigonal Planar Variation

  18. The Second Molecular Shape Of The Trigonal Planar Electron-group Arrangement. Examples: SO2, O3

  19. Bent • Trigonal Planar variation #1 • 2 atoms attached to central atom • 1 lone pair • Bond angle = <120 • Type: AX2E • Ex. : SO2

  20. Redneck Innovations: When you gotta go…..

  21. Tetrahedral • 4 atoms attached to central atom • 0 lone pairs • Bond angle = 109.5o • Type: AX4 • Ex. : CH4

  22. Tetrahedral • Carbon tetrachloride CCl4

  23. 2 Tetrahedral Variations

  24. The Three Molecular Shapes Of The Tetrahedral Electron-group Arrangement. Examples: CH4, SO42- NH3 PF3 H2O OF2

  25. Trigonal Pyramidal • Tetrahedral variation #1 • 3 atoms attached to central atom • 1 lone pair • Bond angle = 107o • Type: AX3E • Ex. : NH3

  26. Trigonal Pyramidal • Nitrogen trifluoride NF3

  27. Bent • Tetrahedral variation #2 • 2 atoms attached to central atom • 2 lone pairs • Bond angle = 104.5o • Type: AX2E2 • Ex. : H2O

  28. Bent • Chlorine difluoride ion ClF2+

  29. National Geographic finds the first fossilized politician!!!!!

  30. Remember the 3 exceptions to the octet rule? • Molecules with atoms near the boundary between metals and nonmetals will tend to have less than an octet on the central atom. (i.e. B, Be, Al, Ga) • Molecules with a central atom with electrons in the 3rd period and beyond will sometimes have more than an octet on the central atom, up to 12, called an extended or expanded octet. • Molecules with an odd number of electrons

  31. 5 Bond Sites on the Central Atom

  32. TrigonalBipyramidal • 5 atoms attached to central atom • 0 lone pairs • Bond angle = • equatorial -> 120o • axial -> 90o • Type: AX5 • Ex. : PF5

  33. TrigonalBipyramidal • Antimony Pentafluoride SbF5

  34. 3 Bipyramidal Variations

  35. The Four Molecular Shapes Of The Trigonal Bipyramidal Electron-group Arrangement. PF5 AsF5 SF4 XeO2F2 XeF2 I3- ClF3 BrF3

  36. See Saw • Trigonal Bipyrimid Variation #1 • Sulfur tetrafluoride SF4

  37. T-Shaped • Trigonal Bipyramid Variation #2 • Chlorine tribromide

  38. Linear • Trigonal Bipyramid Variation #3 • Xenon difluoride XeF2

  39. One of my former students on a hunting trip!!

  40. 6 Bond Sites on the Central Atom

  41. Octahedral • 6 atoms attached to central atom • 0 lone pairs • Bond angle = 90o • Type: AX6 • Ex. : SF6

  42. Octahedral • Sulfur hexafluoride SF6

  43. 2 Octahedral Variations

  44. The Three Molecular Shapes Of The Octahedral Electron-group Arrangement. SF6 IOF5 IF5 XeOF4 XeF4 (BrF4)-

  45. Square Pyramidal • Octahedral Variation #1 • Chlorine pentafluoride ClF5

  46. Square Planar • Octahedral Variation #2 • Xenon tetrafluoride XeF4

  47. Octahedral • Do not need to know: • T-shape • Linear

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