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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. VSEPR Theory. Redneck Innovations. Molecular 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

  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. 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. The Single Molecular Shape Of The Linear Electron-group Arrangement. Examples: CS2, HCN, BeF2

  9. Class Shape The Two Molecular Shapes Of The Trigonal Planar Electron-group Arrangement. Examples: SO2, O3, PbCl2, SnBr2 Examples: SO3, BF3, NO3-, CO32-

  10. 1220 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. 1200 larger EN 1200 ideal greater electron density

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

  12. The Three Molecular Shapes Of The Tetrahedral Electron-group Arrangement. Examples: CH4, SiCl4, SO42-, ClO4- NH3 PF3 ClO3 H3O+ H2O OF2 SCl2

  13. The Four Molecular Shapes Of The Trigonal Bipyramidal Electron-group Arrangement. PF5 AsF5 SOF4 SF4 XeO2F2 IF4+ IO2F2- XeF2 I3- IF2- ClF3 BrF3

  14. The Three Molecular Shapes Of The Octahedral Electron-group Arrangement. SF6 IOF5 BrF5 TeF5- XeOF4 XeF4 ICl4-

  15. Let’s Review VSEPR Theory • Predicts the molecular shape of a bonded molecule • Electrons around the central atom arrange themselves as far apart from each other as possible • Unshared pairs of electrons (lone pairs) on the central atom repel the most • So only look at what is connected to the central atom

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

  17. Let’s Consider a Few More Examples:6 Types of Molecules with no Unshared Pairs of Electrons

  18. Linear • 2 atoms attached to central atom • 0 unshared pairs (lone pairs) • Bond angle = 180o • Type: AB2 • Ex. : BeF2

  19. 3 exceptions to the octet rule • Molecules with an odd number of electrons • 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.

  20. Linear • Carbon dioxide CO2

  21. Trigonal Planar • 3 atoms attached to central atom • 0 lone pairs • Bond angle = 120o • Type: AB3 • Ex. : AlF3

  22. Trigonal Planar • Boron Trifluoride BF3

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  24. Tetrahedral • 4 atoms attached to central atom • 0 lone pairs • Bond angle = 109.5o • Type: AB4 • Ex. : CH4

  25. Tetrahedral • Carbon tetrachloride CCl4

  26. TrigonalBipyramidal • 5 atoms attached to central atom • 0 lone pairs • Bond angle = • equatorial -> 120o • axial -> 90o • Type: AB5 • Ex. : PF5

  27. TrigonalBipyramidal • Antimony Pentafluoride SbF5

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  29. Octahedral • 6 atoms attached to central atom • 0 lone pairs • Bond angle = 90o • Type: AB6 • Ex. : SF6

  30. Octahedral • Sulfur hexafluoride SF6

  31. Examples of Molecules with Both Paired and Unshared (lone) Pairs of Electrons around the Central Atom.

  32. Trigonal Planar • Boron Trifluoride BF3

  33. Bent • Trigonal Planar variation #1 • 2 atoms attached to central atom • 1 lone pair • Bond angle = <120 • Type: AB2E • Ex. : SO2

  34. Tetrahedral • Carbon tetrachloride CCl4

  35. Trigonal Pyramidal • Tetrahedral variation #1 • 3 atoms attached to central atom • 1 lone pair • Bond angle = 107o • Type: AB3E • Ex. : NH3

  36. Trigonal Pyramidal • Nitrogen trifluoride NF3

  37. Bent • Tetrahedral variation #2 • 2 atoms attached to central atom • 2 lone pairs • Bond angle = 104.5o • Type: AB2E2 • Ex. : H2O

  38. Bent • Chlorine difluoride ion ClF2+

  39. TrigonalBipyramidal • Antimony Pentafluoride SbF5

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

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

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

  43. Octahedral • Sulfur hexafluoride SF6

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

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

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

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