To understand molecular structure and bond angles

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Objectives

1. To understand molecular structure and bond angles
   
2. To learn to predict molecular geometry from the
   number of electron pairs
3. To learn to apply the VSEPR model to molecules
   with double bonds

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A. Molecular Structure

• Three dimensional arrangement of the atoms in a
  molecule
• Water - bent

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A. Molecular Structure

• Linear structure atoms in a line

• Carbon dioxide

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A. Molecular Structure

• Trigonal planar atoms in a triangle

• BF3

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A. Molecular Structure

• Tetrahedral structure

• methane

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B. The VSEPR Model

• Valence shell electron pair repulsion (VSEPR)
  model
• Molecular structure is determined by minimizing
  repulsions between electron pairs

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B. The VSEPR Model
Two Pairs of Electrons

• BeCl2

• 180o - linear

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B. The VSEPR Model
Three Pairs of Electrons

• BF3

• 120o trigonal planar

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B. The VSEPR Model
Four Pairs of Electrons

• CH4

• 120o tetrahedral

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B. The VSEPR Model
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B. The VSEPR Model
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C. Molecules with Double Bonds
When using VSEPR model to predict molecular
geometry of a molecule

• a double bond is counted the same as a single
  electron pair