How to Calculate the Formal Charge

Free formal charge calculator with step-by-step explanation for Lewis structures.

Formal Charge Equation

If you are searching how to calculate formal charge, use this standard equation:

Formal Charge (FC) = V - N - (B / 2)

  • V = valence electrons in the neutral atom
  • N = nonbonding (lone-pair) electrons
  • B = bonding (shared) electrons

How to calculate formal charge from Lewis structure

  1. Draw the correct Lewis structure.
  2. Pick one atom and count lone-pair electrons on it.
  3. Count all bonding electrons connected to it.
  4. Apply FC = V - N - (B / 2).
  5. Repeat for all atoms and compare structures.

Stable Lewis Structures

A stable structure typically has formal charges as close to zero as possible. If charges must exist, the negative charge should reside on the most electronegative atom.

Example: How to calculate the formal charge of an atom

For oxygen in many Lewis structures: V = 6, N = 4, B = 4.

FC = 6 - 4 - (4/2) = 6 - 4 - 2 = 0

Frequently Asked Questions

Share this tool:

Was this tool helpful?

Comments

Loading comments...

Check Out Other Popular Tools