Section 8.5 and 8.6 Molecular Geometry and Polarity
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Transcript of Section 8.5 and 8.6 Molecular Geometry and Polarity
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Section 8.5 and 8.6Molecular Geometry and Polarity
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Molecular Geometry and Polarity
In these sections…
a. VSEPR Shapesb. Molecular Shapesc. Molecular Polarity
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Big Picture: What are the shapes of molecules.
Lewis # Structural Electron-Pair Molecular Structure Pairs Geometry Geometry Polarity
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Valence Shell Electron-Pair Repulsion Theory(VSEPR)
Valence electron pairs repel one another.
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Valence Shell Electron-Pair Repulsion Geometries
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# Structural Pairs = # bonded + # lone on Central Atom atoms pairs
Determining Electron-Pair Geometry - Find Number of Structural Electron Pairs
# pairs EPG2 linear3 trigonal planar4 tetrahedral5 trigonal bipyramidal6 octahedral
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Determining Molecular Geometry - Electron-Pair Geometry, ignoring Lone Pair Positions
no lone pairs 1 lone pair
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Determining Molecular Geometry - Electron-Pair Geometry, ignoring Lone Pair Positions
no lone pairs 1 lone pair 2 lone pairs
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Determining Molecular Geometry - Electron-Pair Geometry, ignoring Lone Pair Positions
no lone pairs 1 lone pair 2 lone pairs 3 lone pairs
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Determining Molecular Geometry - Electron-Pair Geometry, ignoring Lone Pair Positions
no lone pairs 1 lone pair 2 lone pairs
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Drawing Shapes on Paper: Wedge-and-Dash Notation
line = in plane of paper/screensolid wedge = coming towards youdashed line = moving away from you
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Deviations from Ideal Molecular Geometry - Lone pairs take up more room
CH4 NH3 H2O
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Molecular Polarity - Net effect of polar bonds in a molecule
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Molecular Polarity - Net effect of polar bonds in a molecule
CO2
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Molecular Polarity - Net effect of polar bonds in a molecule
NH3
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Molecular Polarity - Net effect of polar bonds in a molecule
CHF3
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Molecular Polarity - Three general rules
1. Fully symmetrical molecules with no lone pairs are nonpolar.
2. Hydrocarbons are nonpolar.
3. Molecules containing N-H or O-H bonds are almost always polar.