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VSEPR Theory

VSEPR Theory. Valence Shell Electron Pair Repulsion. 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

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VSEPR Theory

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  1. VSEPR Theory Valence Shell Electron Pair Repulsion

  2. 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

  3. 6 Types of Molecules with no Unshared Pairs of Electrons

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

  5. 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.

  6. Linear • Carbon dioxide CO2

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

  8. Trigonal Planar • Boron Trifluoride BF3

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

  10. Tetrahedral • Carbon tetrachloride CCl4

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

  12. Trigonal Bipyramidal • Antimony Pentafluoride SbF5

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

  14. Octahedral • Sulfur hexafluoride SF6

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

  16. Tetrahedral • Carbon tetrachloride CCl4

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

  18. Trigonal Pyramidal • Nitrogen trifluoride NF3

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

  20. Bent • Chlorine difluoride ion ClF2+

  21. Trigonal Bipyramidal • Antimony Pentafluoride SbF5

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

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

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

  25. Octahedral • Sulfur hexafluoride SF6

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

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

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

  29. Bent • Nitrogen dioxide NO2

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