2. V alence S hell E lectron P air R epulsion Theory Planar triangular Tetrahedral Trigonal pyramidal Bent

3. VSEPR theory assumes that the shape of a molecule is determined by the repulsion of electron pairs. Molecular Shape

4. VSEPR Theory Based on Electron Dot (Lewis structures) Theory predicts shapes of compounds abbreviated VSEPR VSEPR (pronounced “vesper”) stands for Valence Shell Electron Pair Repulsion VSEPR predicts shapes based on electron pairs repelling (in bonds or by themselves) Electrons around central nucleus repel each other. So, structures have atoms maximally spread out

5. VSEPR overview Each shape has a name (you will have to know these ) Names of Shapes: tetrahedral trigonal pyramidal Bent Linear trigonal planar

6. Triangular PlanarTetrahedral Trigonal pyramidal Linear Bent or V Models

7. methane, CH 4 Bonds are all evenly spaced electrons 109.5° Tetrahedral

8. Less repulsion between the bonding pairs of electrons.. ammonia NH 3.. Trigonal Pyramidal

9. .. 109.5° (109.5°) 109.5° (107°) 109.5° (104.5°) water, H 2 O

10. ..

11. Bent or V 2 unshared pairs of e’s at top of O repel bonds and force them to bend

12. molecular geometry. H 2 CO

13. molecular geometry. H 2 CO

14. VSEPR shape orbitals tetrahedral planar linear sp 3 sp 2 sp

15. tetrahedral Methane (CH 4 ) simple hydrocarbon. Shape is not planar but tetrahedral.

16. C H H H H tetrahedral

17. ? EX : Roth pond

18. Methane gas, CH 4

19. MoleculeLewis StructureNumber of electron pairs CH 4 NH 3 SHAPE Tetrahedral Trigonal Pyramidal 4 4 (3 shared 1 lone pair)

20. MoleculeLewis StructureNumber of electron pairs H2OH2O CO 2 SHAPE Bent or V 4 (2 shared 2 lone pairs) 2 Linear

21. MoleculeLewis StructureNumber of electron pairs BeCl 2 BF 3 SHAPE 2 3 Linear Trigonal Planar

22. Fluorine is the Base of Comparison

23. Which atom attracts e- more? H ― Cl δ+δ+δ+δ+ δ-δ-δ-δ- electronegativities 2.1 3.0 C = O ― ― H H 2.53.5 2.1 2.1 O = C = O

24. POLAR MOLECULES POLAR MOLECULES = uneven distribution of charge. negativeslightly positive Creating poles. 1 side of molecule is negative ; one side is slightly positive. * Creating poles. NON-POLAR MOLECULES NON-POLAR MOLECULES = no difference in charge on outside of molecule. Electrons are evenly distributed. Uniform charge on outside of molecule.

25. Predict the polarity of CH 4 (methane) bonds Step 1: Determine polarity of bonds Bonds Bonds are evenly spaced out. If bonds making up a molecule are non-polar, then the molecule is non-polar. Therefore, CH 4 is a non-polar molecule. molecule Step 2: Determine polarity of molecule

26. Carbon dioxide. bonds Step 1: Determine polarity of bonds If bonds making up a molecule are polar, then the molecule may be polar or non-polar, depending on its shape. Which atom attracts electrons more? Molecule Step 2: Determine polarity of Molecule (shape is linear) O = e- pulled toward

27. The center of the positive charges in located on the carbon atom The center of the negative charge is also located on the carbon atom. non-polar. Since center of both the positive and negative charge are located in the same spot in the molecule, there is no difference in overall charge) so the molecule is non-polar.

28. Look at sulfur dioxide. Step 1: Determine polarity of bonds Center of positive charge is on the sulfur atom. While the center of negative charge is located ½ way between the two oxygen atoms. Since polarity of the bonds and shape of the molecule result in an uneven distribution of charge – SO 2 is a polar molecule. Which atom attracts more e-(s)?

29. Now that you have seen how to apply the two steps to determine the polarity of molecules, see if you can predict the polarity of the following: H 2 O PH 3 CCl 4 Ammonia (NH 3 ) SO 3 CH 3 Cl

30. H 2 O (Water) Step 1: Polarity of bonds Based on electronegativity difference between H and O, bond is polar Step 2: Shape of molecule Based on VSEPR theory, water is bent. Center of positive charge is between the two hydrogen, and center of negative charge on oxygen. WATER is a POLAR molecule.

31. PH 3 Step 1: Polarity of bonds Based on electronegativity difference between H and P, bonds are polar Trigonal Pyramidal 1 unshared pair around central Atom 3 shared bond Polar Molecule…

32. NH 3 (Ammonia) Step 1: Polarity of bonds Based on electronegativity difference between H and N, bond is polar Step 2: Shape of molecule Based on VSEPR theory, ammonia has a trigonal pyramidal shape. Center of positive charge is between hydrogen atoms, and center of negative charge on oxygen. AMMONIA is a POLAR molecule.

33. CCl 4 (carbon tetrachloride) Step 1: Polarity of bonds Based on electronegativity difference between C and Cl, bonds are polar Step 2: Shape of molecule Based on VSEPR theory, CCl 4 has a tetrahedral shape. Center of positive charge is on carbon, and center of negative is also on the carbon. No separation of charge. Carbon tetrachloride is a NON- POLAR molecule.

34. SO 3 (Sulfur trioxide) Step 1: Polarity of bonds Based on electronegativity difference between S and O, bond is polar Step 2: Shape of molecule Based on VSEPR theory, SO 3 is trigonal planar. Center of positive charge is on the sulfur, and center of negative charge is between the oxygen atoms (also on S). SO 3 a NON- POLAR molecule.

35. CH 3 Cl (Chloromethane) Step 1: Polarity of bonds C-H bonds are non-polar, C-Cl bon is polar Step 2: Shape of molecule Based on VSEPR theory, CH 3 Cl is tetrahedral. Cl end of bond is negative, while C end of bond is positive. There is a net separation of charge so molecule is POLAR.

36. Solids Review