Molecular Geometry

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Chapter 9

• Molecular Geometry
• VSEPR
• Polarity
• Orbital Overlap
• Hybrid Orbitals

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MOLECULAR SHAPES
CCl4 3-D Atomic Arrangement
Specific Bond Lengths and Bond Angles
Tetrahedral Shape determined by Lewis Structure
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MOLECULAR SHAPES
Molecular shape is determined by VSEPR
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VSEPR

• Valence Shell Electron Pair Repulsion
• Draw the Lewis diagram showing all LPs BPs,
  then count the electron domains
• An Electron Domain is either
• one lone pair
• one covalent bond (of any bond order)
• Arrange electron domains about each atom
• Each electron domain tries to be as far away from
  the other electron domains as possible

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VSEPR - Electron Domain Geometry

• Table 9.1

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VSEPR - Electron Domain Geometry

• Table 9.1

2 axial
3 equatorial
Homepage Extras
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VSEPR - Molecular Geometry

• Table 9.2

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VSEPR - Molecular Geometry

• Table 9.2

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VSEPR - Molecular Geometry

• Table 9.3

Lone Pairs in a Trigonal Bipyramid always occupy
the equatorial positions
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VSEPR - Molecular Geometry

• Table 9.3

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VSEPR - Molecular Geometry

• Summary

A Central Atom B Peripheral Atom X Lone Pair
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VSEPR - Molecular Geometry

• Complex Molecules

The geometry of each Central Atom is determined
by VSEPR
EDG Tetrahedral MG Bent
EDG Tetrahedral MG Tetrahedral
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Bond Polarity

• Chapter 8, pg. 314 ?H-F?-
• Bond Pair - two atoms joined by a bond
• Bond Dipole
• Most electronegative atom of bond pair is
  Negative
• Least electronegative atom of bond pair is
  Positive
• Dipole Moment depends on
• Difference in electronegativity
• Bond length

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Molecule Polarity

• Diatomic molecule (only one bond)
• Molecule Polarity Bond Polarity
• Polyatomic molecule (two or more bonds)
• Molecule Polarity Vector Sum of bond dipoles
• Vector Sum is like tug-o-war

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Molecule Polarity

• Fig 9.11 9.12 tug-o-war

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Molecule Polarity

• Fig 9.13 tug-o-war

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MOLECULAR SHAPES

• Molecular Shape Predicted by VSEPR
• Covalent Bonds Formed by Orbital Overlap
• Orbital Geometry
• predicted by VSEPR
• determined by Hybridization

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Orbital Overlap

• Figure 9.14

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Orbital Geometry

• Trigonal Planar sp2 hybridization
• (similar to figure 9.18)

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Orbital Geometry

• Tetrahedral sp3 hybridization
• (similar to figure 9.20)

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Orbital Geometry

• Table 9.4

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Orbital Geometry

• Table 9.4

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Summary
Ch 10