1. MOLECULAR GEOMETRY Topic # 18

2. Molecular Geometry
Molecules of different subtances have diverse shapes. Atoms attach to one another in various geometric arrangements. The overall molecular shape of a molecule is determined by its bond angles in three dimensions. The shape of a molecule is very important for its physical and chemical properties.

3. Valence Shell Electron Pair Repulsion (VSEPR) Theory
It is a method for predicting the shape of a molecule from the knowledge of the groups of electrons around a central atom.

5. Electron pairs (bonding and nonbonding electrons) repel one another, as a result , the electron pairs remain as far apart as possible from another as possible to minimize the repulsion.
Two electron pairs in the valence orbital are arranged linearly
Three electron pairs are organized in a trigonal planar arrangement
Four electron pairs are organized in a tetrahedral arrangement
The repulsion of lone pair electrons is grater than the repulsion of bond pair electrons

6. Electron pairs assume orientations about an atom to minimize repulsions.

7. question: predict the shape of CO2 HCN CH4, NH3 SO2 PCl5, SF6 and H2O by using VSEPR theory.

8. question: predict the shape of CO2 HCN CH4, NH3 SO2 PCl5, SF6 and H2O by using VSEPR theory.

9. lone pair -lone pair  lone pair e-bond pair  bond pair-bond pair
The nonbonding electron pairs are as important as bonding electron pairs in determining the structure.
The bond angles decrease as the number of nonbonding electron pairs increases
Repulsion strengths
lone pair -lone pair  lone pair e-bond pair  bond pair-bond pair