Chemical Bonding II: Molecular Geometry and Hybridization of Atomic Orbitals Chapter 10

Chapter 10 Topics Valence Bond Theory & Molecular Geometry Dipole moments Hybridization Sigma and pi bond Bonding: Orbitals

VPT Theory and shape of molecules (Electron groups want to be as far as possible from each other) B Cl.. S O O N H H H H H H H C Br F F F F F.. Cl F F F.. S F FF F F F P Cl OO C.. O H H S F F F F I I I Xe F F F F.. 2 groups of valnece e - 3 groups of valnece e - 4 groups of valnece e - 5 groups of valnece e - 6 groups of valnece e - MX 2 MX 3 MX 2 E MX 3 E MX 4 MX 5 MX 6 MX 2 E 2 MX 4 E MX 3 E 2 MX 2 E 3 MX 5 E MX 4 E 2 Linear Planar Triangular V-Shaped Nonlinear bent Tetrahedral Trigonal Pyramidal Nonlinear Bent V-shaped Unsymmetrical Or distorted tetrahedron Trigonal Bipyramidal T-Shaped Octahedral Square Pyramidal Planar Square

Cl Be 2 atoms bonded to central atom 0 lone pairs on central atom

B Cl.. S O O N H H H H H H H C Br F F F F F.. Cl F F F.. S F FF F F F P Cl OO C.. O H H S F F F F I I I Xe F F F F.. 2 groups of valnece e - 3 groups of valnece e - 4 groups of valnece e - 5 groups of valnece e - 6 groups of valnece e - MX 2 MX 3 MX 2 E MX 3 E MX 4 MX 5 MX 6 MX 2 E 2 MX 4 E MX 3 E 2 MX 2 E 3 MX 5 E MX 4 E 2 Linear Planar Triangular V-Shaped Nonlinear bent Tetrahedral Trigonal Pyramidal Nonlinear Bent V-shaped Unsymmetrical Or distorted tetrahedron Trigonal Bipyramidal T-Shaped Octahedral Square Pyramidal Planar Square Not Polar No Dipole Moment Not P No D PDPD Not P No D PDPD PDPD PDPD Not P No D Not P No D PDPD PDPD Not P No D Not P No D Dipole moments and polar molecule

square planar Xe FF FF bent H O H T-shaped Cl F F F square pyramidal Br FF FF F

Q) What are the molecular geometries of SO 2 and SF 4 ? SO O AB 2 E bent S F F F F AB 4 E distorted tetrahedron

Sa. Ex. 8.12: Predict the geometry of PCl 5, PCl 4 +, PCl 6 - Sa. Ex. 8.13: Predict the geometry of XeF 4

Q) Which of the following molecules have a dipole moment? H 2 O, CO 2, SO 2, and CH 4 O H H dipole moment polar molecule S O O CO O no dipole moment nonpolar molecule dipole moment polar molecule C H H HH no dipole moment nonpolar molecule

Q) Does CH 2 Cl 2 have a dipole moment?

For NH 3 N – 1s 2 2s 2 2p 3 3 H – 1s 1 Q) 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 NH 3 be? If use the 3 2p orbitals predict 90 0 Actual H-N-H bond angle is Hybridization

Hybridization – mixing of two or more atomic orbitals to form a new set of hybrid orbitals. 1.Mix at least 2 nonequivalent atomic orbitals (e.g. s and p). Hybrid orbitals have very different shape from original atomic orbitals. 2.Number of hybrid orbitals is equal to number of pure atomic orbitals used in the hybridization process. 3.Covalent bonds are formed by: a.Overlap of hybrid orbitals with atomic orbitals b.Overlap of hybrid orbitals with other hybrid orbitals

Number of group of electrons HybridizationExamples sp sp 2 sp 3 sp 3 d sp 3 d 2 BeCl 2 BF 3 CH 4, NH 3, H 2 O PCl 5 SF 6 Q) How do I predict the hybridization of the central atom? Count the number of group of electrons

SP

SP 2

SP 3

Sigma and pi bond

Sigma (  ) and Pi Bonds (  ) Single bond 1 sigma bond Double bond 1 sigma bond and 1 pi bond Triple bond 1 sigma bond and 2 pi bonds Q) How many  and  bonds are in the acetic acid (vinegar) molecule CH 3 COOH? C H H CH O OH  bonds = = 7  bonds = 1

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