Chem 161-2011 Lecture 12, Chapter 7

Chem 161-2011 Lecture 12, Chapter 7 - CHEMISTRY 161-2011...

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Chem 161-2011 Lecture 12 1 CHEMISTRY 161-2011 LECTURE 12 CHAPTER 7 MOLECULAR GEOMETRY AND BONDING THEORIES ANNOUNCEMENTS E-MAIL EXAMS Quiz 2 starts next Tuesday, October 18th. The quiz will cover 6.1-7.4 Days Emphasis T and W 10/19 and 10/20 Chapt. 6 Th and F 10/21 and 10/22 6.4-7.2 M 10/24 6.5-7.4
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Chem 161-2011 Lecture 12 2 PLAN FOR TODAY Molecular Geometry The VSEPR model Electron-domain geometry and molecular geometry Deviation from ideal bond angles Geometry of molecules with more than one central atom Molecular Geometry and Polarity Valence Bond Theory Hybridization of Atomic Orbitals Hybridization of s and p orbitals Hybridization of s, p, and d oritals Hybridization in molecules containing multiple bonds Bonding Theories and Descriptions of Molecules with Delocalized Bonding
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Chem 161-2011 Lecture 12 3 Sit close to see the VSEPR models.
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Chem 161-2011 Lecture 12 4 VSEPR Valence Shell Electron Pair Repulsion Electron pairs surrounding a central atom keep as far away from each other as possible in order to minimize electron repulsion.
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Chem 161-2011 Lecture 12 6 Molecular Polarity No No No No Yes Yes Yes **Assuming bonds are polar and terminal atoms are identical. < < sp (+ 2 p orbitals non-hybridized) Hybridization sp 2 (+ 1 p orbial non-hybridized) sp 2 + (1 p orbital non-hybridized) sp 3 sp 3 sp 3 sp 3 d * Number of bonding and non-bonding electron pairs, not including π electron pairs; previously referred to as “number of electron domains”. ** First remove atoms from equatorial bonds, then from axial bonds. < domains* ET: VSEPR = Valence-shell electron pair repulsion; ET: Use BeH 2 and BH 3 , CH 4 square planar and CH 4 tetrahedral as models. ET: Show models of “electron domains, i.e., CH 2 with a non-bonding electron pair, CH 2 -O, and CH 2 =O, demonstrating equal electron group geometry. ET: Discuss “Molecular Polarity” analogous to sled dog’s pulling in various directions in Susan Butcher’s Iditarod race in Alaska; use CH 2 O as an example. domain Electron- domain Geometry AX 2 (E) AX 3 (E) AX 2 (E 2 ) ** or bent or bent
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Chem 161-2011 Lecture 12 7 No No No Yes Yes Yes Molecular Polarity** **Assuming bonds are polar and terminal atoms are identical < < < ,180 O 180 O Hybridization sp 3 d sp 3 d sp 3 d sp 3 d 2 sp 3 d 2 sp 3 d 2 * Number of bonding and non-bonding electron pairs, not including π electron pairs * < < < < or square bipyramidal or square bipyramidal domains* or square bipyramidal or square bipyramidal Electron- domain Geometry AX 4 (E) AX 3 (E 2 ) AX 2 (E 3 ) AX 5 (E) AX 4 (E 2 )
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Chem 161-2011 Lecture 12 8 POLARITY OF MOLECULES SUMMARY “SYMMETRY KILLS POLARITY” All of the parent molecules are vectorially symmetrical. Therefore they are all non-polar. All of the children molecules (except 2) are vectorially asymmetrical. Therefore, they are all (except 2) polar. The two non-polar children molecules are: Trigonal bipyramidal – 3 = linear (symmetrical).
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Chem 161-2011 Lecture 12, Chapter 7 - CHEMISTRY 161-2011...

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