So this dot structure might look like we're done, but we have a lot of formal charges. Formal Charge = [V – N – (B/2)] In this formula, V stands for the number of valence electrons of that atom (these are the electrons that revolve in the outermost orbit of the atom), N stands for the number of non-bonded electrons, and B stands for the number of electrons that are a … And usually molecules like to have-- like to minimize the formal charge. For example, let’s calculate the formal charge on an oxygen atom in a carbon dioxide (CO 2) molecule: FC = 6 valence electrons – (4 non-bonding valence electrons + 4/2 electrons in covalent bonds) FC = 6 – 6 = 0. We have -1, plus 2, and -1. formal charge= # valence shell electrons (free atom)−# lone pair electrons− 1 2# bonding electrons formal charge = # valence shell electrons (free atom) − # lone pair electrons − 1 2 # bonding electrons. After applying the rules outlined above to each atom in the Lewis structure, we will then use the following formula to calculate the formal charge of each atom: How to calculate formal charge. FORMAL CHARGE is a concept used to determine the most probable Lewis structure. Chad breaks down a simple way to remember the formula for calculating Formal Charge (Normal Valence minus "dots and lines.") [Formal charge] H = 1 – (1/2) × 2 – 0 = 0 ⇒ This applies to each hydrogen. The oxygen atom in carbon dioxide has a formal charge of 0. These hydrogens are all zero. The formula for the formal charge is: Let us start with something simple, like carbon dioxide. Its Lewis structure looks like this: Step 1: Calculate the Formal Charge of CCarbon (C) is in group 14, so that means it has 4 valence electrons. And so if there's any way to get this formal charge as close to 0 as possible, that would be the preferred dot structure. Formal charge = group number of atom of interest - electrons in the circle of atom of interest The sum of the formal charges of each atom must be equal to the overall charge of the molecule or ion. Once we add all the formal charges for the atoms in the Lewis structure, we should get a value equal to the actual charge of the molecule or ion. To learn more about finding the formal charge, review the corresponding lesson Calculating Formal Charge: Definition & Formula. The formal charge of an atom in a Lewis formula is the hypothetical charge you obtain by assuming that bonding electrons are equally shared between bonded atoms and that the electrons of each lone pair (nonbonding pair) belong completely to one atom. Formal Charge of H = (1 valence e-) - (0 lone pair e-) - (1/2 x 2 bond pair e-) = 0. We can double-check formal charge calculations by determining the sum of … In this example, the nitrogen and each hydrogen has a formal charge of zero. Struggling with Formal Charges? Here’s the formula for figuring out the “formal charge” of an atom: Formal charge = [# of valence electrons] – [electrons in lone pairs + 1/2 the number of bonding electrons] This formula explicitly spells out the relationship between the number of bonding electrons and their relationship to how many are formally “owned” by the atom. [Formal charge] C = 4 – (1/2) × 6 – 0 = 4 – 3 – 0 = +1 Carbon dioxide has one carbon atom and two oxygen atoms.