1. Molecular Geometry
VSEPR and beyond!

2. Molecular Geometry Three dimensional arrangment of atoms
Molecular polarity determined by geometry and polarity of bonds
Molecular polarity: distribution of molecular charge
Influences forces between molecules
Two ideas explain and describe geometry:
VSEPR theory
Hybridization

3. VSEPR Valence shell electron pair repulsion
Repulsion between valence pairs causes them to be separated as far as possible
Separation of electron pairs (and bonds) creates the geometry of the molecule

4. VSEPR: Steps Find the Lewis structure Analyze the structure:
A is central atom
B represents atoms bonded to A
E represents lone pairs on A
Use Table 6-5 on page 186 to determine geometry

5. VSEPR Example Sample Problem 6-5 AlCl3
Molecule is AB3, so is trigonal-planar
CBr4
Molecule is AB4, so is tetrahedral

6. VSEPR Example: Lone Pairs
Only lone pairs on central atom matter!
Sample Problem 6-6
Use VSEPR to predict the shape of a molecule of CO2
AB2, so is linear
ClO3-
AB3E, so is trigonal pyramidal