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VSEPR Theory

VSEPR Theory. The shape of molecules. VSEPR Theory. Valence shell electron pair repulsion (VSEPR) theory Pronounced “Vesper”. VSEPR Theory. VESPR- is a model that helps us determine the geometric 3D shape of a molecule. VSEPR Theory.

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VSEPR Theory

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  1. VSEPR Theory The shape of molecules

  2. VSEPR Theory Valence shell electron pair repulsion (VSEPR) theory Pronounced “Vesper”

  3. VSEPR Theory VESPR- is a model that helps us determine the geometric 3D shape of a molecule

  4. VSEPR Theory • Only valence e- around the central atom determines molecular shape (valence shell) • The lone electron pairs and bonded electron pairs around the central atom want to be as far away from each other as possible (electron pair repulsion)

  5. VSEPR Steps • Draw Lewis structure for molecule • Count number of lone e- pairs & bonded e- pairs around central atom • describe molecular shape

  6. VSEPR Steps • First draw Lewis dot structure. • 4 bonded electron pairs around central atom • Shape tetrahedral

  7. 2 Attachments • If there are 2 attachments to the central atom, the shape is linear • Bond angle = 180°

  8. 3 Attachments • If there are 3 attachments to central atom the shape will be Trigonal Planar (Flat Triangle) • Bond angle = 120°

  9. 3 total electron pair attachments but one is lone pair • imagine you have 3 electron pairs, but one is just a lone pair what would it look like then?

  10. 4 Attachments • If there are 4 electron bonding pairs, the shape will be tetrahedral • Bond angle = 109.5°

  11. 4 total electron pair attachments3 are bonded pairs 1 is lone pair • What if 1 of the electron pairs is a lone pair? What would it look like then? • Trigonal Pyramidal (Triangular Pyramid)

  12. 4 electron pair attachments 2 bonded and 2 lone pair

  13. Practice Determine the molecular shape for the following compound NCl3

  14. Practice Determine the molecular shape for the following compound NCl3 First draw Lewis Dot Next count number of bonding pairs and lone pairs Then refer to your chart Which structure has 3 bonding pairs and one lone pair? Trigonal Pyramidal

  15. Practice Determine the molecular shape for the following compound NBr3

  16. END Finis Stop here

  17. 5 electron pairs • If there are 5 electron pairs the shape will be Trigonal Bipyramidal • Bond angles = 90º & 120º

  18. 5 electron pairs • What is there is 1 lone pair (invisible) • Seesaw

  19. 5 electron pairs • What is there are 2 lone pairs (invisible) • T-shaped

  20. 6 electron pairs • If there are 6 electron pairs the shape will be octahedral • Bond angle = 90°

  21. 6 electron pairs • What if there is 1 lone pair (invisible)? • Square pyramidal

  22. 6 electron pairs • What if there are 2 lone pairs (invisible) • Square planar

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