How to calculate formal charge of an atom?

FC = valence electrons - nonbonding electrons - (bonding electrons / 2).

What is a good formal charge in a Lewis structure?

The best structure minimizes formal charges and puts negative charge on the more electronegative atom.

How to Calculate the Formal Charge

Q: How to calculate formal charge from Lewis structure?

Count valence electrons, subtract lone-pair electrons and half of shared bonding electrons.

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

Atom Preset (Optional)

Valence Electrons (V)

Nonbonding (Lone-Pair) Electrons (N)

Bonding (Shared) Electrons (B)

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

Draw the correct Lewis structure.
Pick one atom and count lone-pair electrons on it.
Count all bonding electrons connected to it.
Apply FC = V - N - (B / 2).
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.

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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

Use the same formula each time: FC = V - N - (B/2). This calculator automates the arithmetic and shows the equation.

Evaluate one atom at a time: count lone-pair electrons on that atom, count shared electrons in its bonds, then apply FC = V - N - (B/2).

Formal charge helps compare Lewis structures and predict the most stable arrangement of electrons in molecules and ions.

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