1. Molecular Geometry

2. *They get as far away from each other as possible!
MOLECULAR GEOMETRY
VSEPR stands for:
Valence Shell Electron Pair Repulsion theory.
Most important factor in determining the shape of the molecule is the repulsion between electron pairs.
Molecules form their shapes to minimize the repulsions of the electrons.
*They get as far away from each other as possible!

3. VSEPR Charts
Use the Lewis Structure to determine the geometry of the molecule.
Focus only on the CENTRAL atom for all molecules! Count the number of electron regions.
Look for REGIONS WHERE ELECTRONS ARE FOUND rather than number of bonds. (Ex: Double and Triple bonds count as 1 region)

4. Lets look at Methane (CH4)
Lets look at Methane (CH4). The molecule is really three dimensional, not planar and flat. C H

5. When models are constructed, they show the bonds, but not the lone pairs of electrons... ..
109.5° (109.5°)
109.5° (107°)
109.5° (104.5°)

6. Some Common Geometries

7. Structure Determination by VSEPR
Water, H2O
1) Looking at the central atom, how many regions are there?
2) How many bonded atoms? How many lone pairs?
The electron pair geometry is TETRAHEDRAL H O ••
2 bond pairs
2 lone pairs
The molecular geometry is BENT.

8. Structure Determination by VSEPR
Ammonia, NH3
The electron pair geometry is Tetrahedral , and the Geometry name is TRIGONAL PYRAMID.