Formal Charges

What are formal charges?

A way of counting electrons that are involved in bonding atoms.

How do you calculate formal charges?

Two simple rules:

1. Non-bonding electrons of a given atom are counted for that atom
2. Bonding electrons are halved between both atoms, i.e. if a pair of electrons are shared between two atoms, one electron is counted for each atom

$Formal \ charge = \left( Total \ valence \ electrons \right) - \left( \char93... ...bonding \ e^{-} \right) - \left( 1/2 \ \char93 \ of \ bonding \ e^{-} \right)$