Covalent Bonding: Molecular Geometry Hybridization of Atomic Orbitals Molecular Orbitals - PowerPoint PPT Presentation

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Covalent Bonding: Molecular Geometry Hybridization of Atomic Orbitals Molecular Orbitals
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Covalent Bonding: Molecular Geometry Hybridization of Atomic Orbitals Molecular Orbitals

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  1. Covalent Bonding:Molecular Geometry Hybridization of Atomic Orbitals Molecular Orbitals

  2. Valence shell electron pair repulsion (VSEPR) model: # of atoms bonded tocentral atom # lone pairs on central atom trigonal planar trigonal planar AB3 3 0 Arrangement ofelectron pairs Molecular Geometry Class trigonal bipyramidal trigonal bipyramidal AB5 5 0 Predict the geometry of the molecule from the electrostatic repulsions between the electron (bonding and nonbonding) pairs. AB2 2 0 linear linear tetrahedral tetrahedral AB4 4 0 octahedral octahedral AB6 6 0 10.1

  3. VSEPR linear tetrahedral trigonal planar trigonal bipyramidal octahedral

  4. VSEPR linear tetrahedral trigonal planar Cl Be Cl trigonal bipyramidal octahedral BF3 CH4 PCl5 SF6

  5. Effects of Lone Pairs H H O H H N H H H C H H lone-pair vs. lone pair repulsion lone-pair vs. bonding pair repulsion bonding-pair vs. bonding pair repulsion > >

  6. # of atoms bonded tocentral atom # lone pairs on central atom trigonal planar Arrangement ofelectron pairs Molecular Geometry bent Class VSEPR trigonal planar trigonal planar AB3 3 0 AB2E 2 1

  7. # of atoms bonded tocentral atom # lone pairs on central atom trigonal pyramidal tetrahedral Arrangement ofelectron pairs Molecular Geometry Class VSEPR tetrahedral tetrahedral AB4 4 0 AB3E 3 1

  8. # of atoms bonded tocentral atom # lone pairs on central atom trigonal pyramidal Arrangement ofelectron pairs Molecular Geometry AB3E 3 1 tetrahedral Class bent tetrahedral O H H VSEPR tetrahedral tetrahedral AB4 4 0 AB2E2 2 2

  9. # of atoms bonded tocentral atom # lone pairs on central atom trigonal bipyramidal distorted tetrahedron Arrangement ofelectron pairs Molecular Geometry Class VSEPR trigonal bipyramidal trigonal bipyramidal AB5 5 0 AB4E 4 1

  10. # of atoms bonded tocentral atom # lone pairs on central atom trigonal bipyramidal distorted tetrahedron Arrangement ofelectron pairs Molecular Geometry AB4E 4 1 Class trigonal bipyramidal T-shaped F F Cl F VSEPR trigonal bipyramidal trigonal bipyramidal AB5 5 0 AB3E2 3 2

  11. # of atoms bonded tocentral atom # lone pairs on central atom trigonal bipyramidal distorted tetrahedron Arrangement ofelectron pairs Molecular Geometry AB4E 4 1 Class trigonal bipyramidal T-shaped AB3E2 3 2 trigonal bipyramidal linear I I I VSEPR trigonal bipyramidal trigonal bipyramidal AB5 5 0 AB2E3 2 3

  12. octahedral octahedral AB6 6 0 # of atoms bonded tocentral atom # lone pairs on central atom square pyramidal octahedral Arrangement ofelectron pairs Molecular Geometry Class F F F Br F F VSEPR AB5E 5 1

  13. octahedral octahedral AB6 6 0 # of atoms bonded tocentral atom # lone pairs on central atom square pyramidal octahedral AB5E 5 1 Arrangement ofelectron pairs Molecular Geometry Class square planar octahedral F F Xe F F VSEPR AB4E2 4 2

  14. What are the molecular geometries of SO2 and SF4? F S F F O O S F Predicting Molecular Geometry • Draw Lewis structure for molecule. • Count number of lone pairs on the central atom and number of atoms bonded to the central atom. • Use VSEPR to predict the geometry of the molecule. AB4E AB2E distorted tetrahedron bent

  15. F H d- d+ Dipole Moments and Polar Molecules electron rich region electron poor region m = Q x r Q is the charge r is the distance between charges 1 D = 3.36 x 10-30 C m

  16. Which of the following molecules have a dipole moment? H2O, CO2, SO2, and CH4 O O S H H H O C H O O C H H dipole moment polar molecule dipole moment polar molecule no dipole moment nonpolar molecule no dipole moment nonpolar molecule

  17. Does CH2Cl2 have a dipole moment?

  18. Chemistry In Action: Microwave Ovens

  19. How does Lewis theory explain the bonds in H2 and F2? Overlap Of 2 1s Bond Dissociation Energy Bond Length 2 2p H2 436.4 kJ/mole 74 pm F2 150.6 kJ/mole 142 pm Sharing of two electrons between the two atoms. Valence bond theory – bonds are formed by sharing of e- from overlapping atomic orbitals.

  20. Change in electron density as two hydrogen atoms approach each other.

  21. If the bonds form from overlap of 3 2p orbitals on nitrogen with the 1s orbital on each hydrogen atom, what would the molecular geometry of NH3 be? Valence Bond Theory and NH3 N – 1s22s22p3 3 H – 1s1 If use the 3 2p orbitals predict 900 Actual H-N-H bond angle is 107.30

  22. Hybridization – mixing of two or more atomic orbitals to form a new set of hybrid orbitals. • Mix at least 2 nonequivalent atomic orbitals (e.g. s and p). Hybrid orbitals have very different shape from original atomic orbitals. • Number of hybrid orbitals is equal to number of pure atomic orbitals used in the hybridization process. • Covalent bonds are formed by: • Overlap of hybrid orbitals with atomic orbitals • Overlap of hybrid orbitals with other hybrid orbitals

  23. Bonding in Methane

  24. Formation of sp3 Hybrid Orbitals Fig. 10.7

  25. Formation of sp3 Hybrid Orbitals

  26. Formation of a CH4 Molecule

  27. Formation of a NH3 Molecule

  28. Stylized Drawing of Valence Bond Theory Predict correct bond angle NH3 CH4 Sigma bond (s) – electron density between the 2 atoms

  29. Formation of sp2 Hybrid Orbitals

  30. Formation of sp2 Hybrid Orbitals

  31. Formation of sp2 Hybrid Orbitals 2pz orbital is perpendicular to the plane of hybridized orbitals

  32. sp2 Hybridization of a C atom

  33. Bonding in Ethylene C2H4 H H C C H H Sigma bond (s) – electron density between the 2 atoms

  34. Bonding in Ethylene C2H4 Pi bond (p) – electron density above and below plane of nuclei of the bonding atoms

  35. Bonding in Ethylene C2H4

  36. Formation of sp Hybrid Orbitals

  37. Formation of sp Hybrid Orbitals

  38. Formation of sp Hybrid Orbitals

  39. Bonding in acetylene C2H2

  40. How do I predict the hybridization of the central atom? Count the number of lone pairs AND the number of atoms bonded to the central atom # of Lone Pairs + # of Bonded Atoms Hybridization Examples 2 sp BeCl2 3 sp2 BF3 4 sp3 CH4, NH3, H2O 5 sp3d PCl5 6 sp3d2 SF6

  41. How many s and p bonds are in the acetic acid (vinegar) molecule CH3COOH? H H C H C O O H Sigma (s) and Pi Bonds (p) 1 sigma bond Single bond 1 sigma bond and 1 pi bond Double bond Triple bond 1 sigma bond and 2 pi bonds s bonds = 6 + 1 = 7 p bonds = 1

  42. Experiments show O2 is paramagnetic O O Drawback of Valence Bond Theory No unpaired e- Should be diamagnetic Molecular orbital theory – bonds are formed from interaction of atomic orbitals to form molecular orbitals.

  43. An analogy between light waves and atomic wave functions Amplitudes of wave functions subtracted. Amplitudes of wave functions added