1. Formal Charge and Molecular Structure

2. Formal Charge Rules Assumptions:
Lone pairs belong only to the atom in question.
Shared electrons are divided equally between the two sharing atoms.

3. Formal Charge Rules
Formal Charge (FC) = (# of v.e-s on a free atom) – (# of v.e-s assigned to the atom in the molecule)
V.e-s assigned to an atom = (# of lone pair electrons) + ½(# of shared electrons)
FC = (# of v.e-s on a free atom) - [(# of lone pair electrons) + ½(# of shared electrons)]

4. Examples
P.406: 73

5. Minimal Formal Charges
The most stable bond structure puts the smallest formal charge on each atom.
As close to zero as possible!
Any negative formal charge should reside on the most electronegative atom in the molecule.
Example: Examine Sample Exercise (p.388)
Examples: P.406: 744