What is formal charge?
Formal charge is a bookkeeping tool chemists use to track electrons in a Lewis structure. It helps identify the most reasonable structure among several possible arrangements of atoms and bonds, and highlights which atom likely carries a positive or negative charge.
How this calculator works
The formal charge on an atom is calculated as:
Formal Charge = (valence electrons of the free atom) − (nonbonding electrons) − (bonding electrons ÷ 2)
Valence electrons are the number an isolated, neutral atom of that element normally has. Nonbonding electrons are the lone pair electrons drawn directly on that atom in the structure. Bonding electrons are the total number of electrons in all bonds around that atom (2 electrons per single bond, 4 per double bond, and so on) — only half of these count toward that atom’s formal charge, since they’re shared.
- The formal charges on all atoms in a valid Lewis structure should add up to the overall charge of the molecule or ion.
- The best Lewis structure usually minimizes formal charges and places any negative formal charge on the more electronegative atom.
This tool is for general chemistry education purposes.