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

2. A. Molecular Structure
Three dimensional arrangement of the atoms in a molecule
Water - bent

3. A. Molecular Structure
Linear structure – atoms in a line
Carbon dioxide

4. A. Molecular Structure
Trigonal planar – atoms in a triangle
BF3

5. A. Molecular Structure
Tetrahedral structure
methane

6. B. The VSEPR Model
Valence shell electron pair repulsion (VSEPR) model
Molecular structure is determined by minimizing repulsions between electron pairs

7. B. The VSEPR Model
Two Pairs of Electrons
BeCl2
180o - linear

8. B. The VSEPR Model
Three Pairs of Electrons
BF3
120o – trigonal planar

9. B. The VSEPR Model
Four Pairs of Electrons
CH4
120o – tetrahedral

10. B. The VSEPR Model

11. B. The VSEPR Model

12. 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