Molecular Geometry (p. 232 – 236)

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Molecular Geometry(p. 232 236)

• Ch. 8 Molecular Structure

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Teacher Notes Why VSEPR?
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A. VSEPR Theory

• Valence Shell Electron Pair Repulsion Theory
• Electron pairs orient themselves in order to
  minimize repulsive forces

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A. VSEPR Theory

• Types of e- Pairs
• Bonding pairs form bonds
• Lone pairs nonbonding e-
• Total e- pairs bonding lone pairs

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A. VSEPR Theory

• Lone pairs reduce the bond angle between atoms

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B. Determining Molecular Shape

• Draw the Lewis Diagram
• Tally up e- pairs on central atom (bonds lone
  pairs)
• double/triple bonds ONE pair
• Shape is determined by the of bonding pairs and
  lone pairs

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C. Common Molecular Shapes 1

• ? Electronic Geometry linear
• Hybridization sp

• 2 total
• 2 bond
• 0 lone

LINEAR 180
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C. Common Molecular Shapes 2
? Electronic Geometry trigonal
planar Hybridization sp2

• 3 total
• 3 bond
• 0 lone

TRIGONAL PLANAR 120
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C. Common Molecular Shapes 3
? Electronic Geometry trigonal
planar Hybridization sp2

• 3 total
• 2 bond
• 1 lone

BENT lt120
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C. Common Molecular Shapes 4
? Electronic Geometry tetrahedral Hybridiza
tion sp3

• 4 total
• 4 bond
• 0 lone

TETRAHEDRAL 109.5
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C. Common Molecular Shapes 5
? Electronic Geometry tetrahedral Hybridiza
tion sp3

• 4 total
• 3 bond
• 1 lone

TRIGONAL PYRAMIDAL 107
lt109.5
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C. Common Molecular Shapes 6
? Electronic Geometry tetrahedral Hybridiza
tion sp3

• 4 total
• 2 bond
• 2 lone

BENT 104.5
lt109.5
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C. Common Molecular Shapes 7
? Electronic Geometry trigonal
bipyramidal Hybridization sp3d

• 5 total
• 5 bond
• 0 lone

TRIGONAL BIPYRAMIDAL 120/90
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C. Common Molecular Shapes 8
? Electronic Geometry trigonal
bipyramidal Hybridization sp3d

• 5 total
• 4 bond
• 1 lone

SEESAW lt120/lt90
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C. Common Molecular Shapes 9
? Electronic Geometry trigonal
bipyramidal Hybridization sp3d

• 5 total
• 3 bond
• 2 lone

T-SHAPE lt90
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C. Common Molecular Shapes 10
? Electronic Geometry trigonal
bipyramidal Hybridization sp3d

• 5 total
• 2 bond
• 3 lone

LINEAR 180
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C. Common Molecular Shapes 11
? Electronic Geometry octahedral Hybridizat
ion sp3d2

• 6 total
• 6 bond
• 0 lone

OCTAHEDRAL 90
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C. Common Molecular Shapes 12
? Electronic Geometry octahedral Hybridizat
ion sp3d2

• 6 total
• 5 bond
• 1 lone

SQUARE PYRAMIDAL lt90
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C. Common Molecular Shapes 13
? Electronic Geometry octahedral Hybridizat
ion sp3d2

• 6 total
• 4 bond
• 2 lone

SQUARE PLANAR 90
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D. Examples

• SeO3

3 total 3 bond 0 lone
E.G. TRIGONAL PLANAR M.G. TRIGONAL PLANAR 120
Hybridization sp2
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D. Examples

• AsH3

4 total 3 bond 1 lone
E.G. TETRAHEDRAL M.G. TRIGONAL
PYRAMIDAL 107 (lt109.5)
Hybridization sp3
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E. Hybridization

• Provides information about molecular bonding and
  molecular shape
• Several atomic orbitals mix to form same total of
  equivalent hybrid orbitals

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E. Hybridization

• Carbon is common example (orbital diagram)
• One of 2s electrons is promoted to 2p
• 4 identical orbitals form sp3 hybridization

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E. Hybridization

• Other types of hybridization
• BeH2 forms
• AlCl3 forms
• SiF4 forms
• KrF4 forms
• SF4 forms

sp sp2 sp3 d2sp3 or sp3d2 dsp3 or sp3d
exceptions
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F. Hybridization Example

• Compare shapes and hybrid orbitals
• PF3 PF5