1. 12.4 Molecular Geometry
Lewis Dot Structures do not represent the actual shape of molecules.
However, Lewis Dot Structures do allow us to predict the shape of the molecule.
Predicting the 3-dimensional shape of a molecule is called molecular geometry.
To correctly predict the shape of a molecule, a correct Lewis structure is essential, including non-bonded electrons.

2. Molecular Geometry
The model used to predict molecular geometry is called VSEPR
Valence
Shell
Electron
Pair
Repulsion
The valence electron pairs surrounding an atom (both bonding and unbonded) repel one another. Consequently, the orbitals containing those electron pairs are oriented to be as far away from each other as possible.

3. Simple Molecular Geometry AXn
Molecular geometry, even for the most difficult structures, can be broken down into a central atom surrounded by terminal atoms.
Tables 7.5 and 7.8 give the possible molecular geometry and angles between bonds for molecules fitting the AXn format.
In order to determine the correct format of AXn, you must make a correct Lewis structure.

4. Primary Molecular Geometries
BeH2 is in format AX2
OH2 is in format AX2E2
The difference is the unshared pairs which changes the molecular geometry.
Linear
molecule
Bent
molecule

5. Primary Molecular Geometries
BF3 is in format AX3
NH3 is in format AX3E
The difference is the unshared pairs which changes the molecular geometry.
Triangular
planar
Triangular
pyramidal

6. Fun With Models
Go to a lab station and inventory the model kits according to the Atom Parts in the ATOMOD 2 Brochure. Let me know if you have less or extras!

7. Draw then make the following molecules
CH4 methane
C2H4 ethene
NH4+ ammonium
CO2 carbon Dioxide