chapter10_ValenceTheory_MolecularOrbital

chapter10_ValenceTheory_MolecularOrbital - Chapter 10...

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Chapter 10 Molecular Shape, Valence Bond Theory and Molecular Orbital Theory 1
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Molecular Shapes The shape of a molecule plays an important role in its reactivity. 2
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Electron Domains Electron pairs around an atom can be referred as electron domains (or electron groups). In a double or triple bond, all electrons shared between those two atoms are on the same side of the central atom; therefore, they count as one electron domain. This molecule has four electron domains around its central atom. 3
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What Determines the Shape of a Molecule? Electron pairs around an atom, whether they be bonding or nonbonding, repel each other. The best arrangement is the one that minimizes the repulsions among them . To minimize the repulsion, electron pairs are placed as far as possible from each other around the central atom. 4
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Valence Shell Electron Pair Repulsion Theory (VSEPR) linear trigonal planar tetrahedral trigonal bipyramidal octahedral 5
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Electron-Domain Geometries To determine the electron domain geometry, count the number of electron domains in the Lewis structure. The geometry will be the one that corresponds to that number of electron domains. 8
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Molecular Geometries The electron-domain geometry is sometimes not the shape of the molecule. The molecular geometry (shape) is defined by the positions of only the atoms in the molecules, not the nonbonding electron pairs. 9
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Linear Electron Domain Geometry 10 In this situation, there is only one possible molecular geometry: linear.
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Trigonal Planar Electron Domain Geometry There are two possible molecular geometries: Trigonal planar Bent 11
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Nonbonding Pairs and Bond Angle Nonbonding pairs (lone pairs) are physically larger than bonding pairs. Therefore, their repulsions are greater; this tends to decrease bond angles in a molecule. 12
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Multiple Bonds and Bond Angles Double and triple bonds place greater electron density on one side of the central atom than do single bonds. Therefore, they also affect bond angles. 13
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Tetrahedral Electron Domain Geometry There are three possible molecular geometries: Tetrahedral, Trigonal Pyramidal, and Bent 14
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Trigonal Bipyramidal Electron Domain Geometry There are two distinct positions in this geometry: Axial Equatorial 15
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Trigonal Bipyramidal Electron Domain Geometry Lower-energy conformations result from having nonbonding electron pairs in equatorial, rather than axial, positions in this geometry. 16
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Trigonal Bipyramidal Electron Domain Geometry There are four possible molecular geometries: Trigonal bipyramidal Seesaw T-shaped Linear 17
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All positions are equivalent in the octahedral electron domain geometry. There are three possible molecular
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chapter10_ValenceTheory_MolecularOrbital - Chapter 10...

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