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Unformatted text preview: 10/27/2011 1 Molecular Geometry and Bonding Theories 7 7.1 VSEPR Model 7.2 Molecular Geometry and Polarity 7.4 Hybridization of Atomic Orbitals 7.5 Hybridization of Molecules Containing Multiple Bonds 7.6 Molecular Orbital Theory A is the central atom surrounded by x B atoms. x can have integer values of 2 to 6. AB x Molecular Geometry Molecular shape can be predicted by using the valence-shell electron-pair repulsion (VSEPR) model. The VSEPR Model Electrons, being negatively charged, repel each other and are most stable when they are separated as much as possible. Electrons are found in various domains . Lone pairs Single bonds Double bonds Triple bonds 2 double bonds 2 electron domains (on central atom) 1 single bond 1 double bond 1 lone pair 3 electron domains (on central atom) 3 single bonds 1 lone pair 4 electron domains (on central atom) Electron-Domain Geometry and Molecular Geometry The basis of the VSEPR model is that electrons repel each other. Electrons will arrange themselves to be as far apart as possible. Arrangements minimize repulsive interactions. 2 electron domains Linear 3 electron domains Trigonal planar Electron-Domain Geometry and Molecular Geometry 5 electron domains Trigonal bipyramidal 6 electron domains Octahedral 4 electron domains Tetrahedral 10/27/2011 2 Electron-Domain Geometry and Molecular Geometry The electron domain geometry is the arrangement of electron domains around the central atom. The molecular geometry is the arrangement of bonded atoms . In an AB x molecule, a bond angle is the angle between two adjacent A-B bonds. Trigonal bipyramidal Octahedral Tetrahedral Linear Trigonal planar 180 120 109.5 90 120 90 Electron-Domain Geometry and Molecular Geometry AB 5 molecules contain two different bond angles between adjacent bonds. Axial positions: perpendicular to the trigonal plane Equatorial positions : three bonds arranged in a trigonal plane. 120 90 Electron-Domain Geometry and Molecular Geometry When the central atom in an AB x molecule bears one or more lone pairs, the electron-domain geometry and the molecular geometry are no longer the same. Electron-Domain Geometry and Molecular Geometry Number of e- domains Number of lone pairs Class e- domain geometry Molecular geometry Example 2 0 AX 2 Linear Linear CO 2 3 0 AX 3 Trigonal planar Trigonal planar H 2 CO 1 AX 2 E Bent SO 2 4 0 AX 4 Tetrahedral Tetrahedral CH 4 1 AX 3 E Trigonal pyramidal NH 3 2 AX 2 E 2 Bent H 2 O Number of e- domains Number of lone pairs Class e- domain geometry Molecular geometry Example 5 0 AX 5 Trigonal bipyramidal Trigonal bipyramidal PCl 5 1 AX 4 E Seesaw SF 4 2 AX 4 E 2 T-shaped ClF 3 3 AX 4 E 3 Linear ICl 2- 6 0 AX 6 Octahedral Octahedral SF 6 1 AX 5 E Square pyramidal BrF 5 2 AX 4 E 2 Square planar XeF 4 Electron-Domain Geometry and Molecular Geometry Determine the molecular geometry by considering the positions of the atoms only....
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This note was uploaded on 02/20/2012 for the course 160 161 taught by Professor Kim during the Fall '08 term at Rutgers.
- Fall '08