Lewis Dot Structure Calculator — Valence Electrons & Bonding

Select a Common Molecule

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Central Atom

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Central Atom Valence Electrons

Surrounding Atom Symbol

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Surrounding Atom Count

Surrounding Atom Valence Electrons

Total Valence Electrons

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Sources & Methodology

Lewis dot structures follow the octet rule (8 electrons per atom, 2 for hydrogen). Total valence electrons = sum of each atom's group valence electrons. Bonding electrons = 2 × number of bonds. Lone pairs fill remaining electrons on each atom to complete octets.

How to Draw Lewis Dot Structures

Lewis dot structures are a fundamental tool in general chemistry that show how valence electrons are distributed in a molecule. The process follows a systematic set of steps.

Step-by-Step Process

Step 1 — Count total valence electrons: Sum the valence electrons for all atoms. Subtract 1 electron for each positive charge; add 1 for each negative charge.
Step 2 — Identify the central atom: Usually the least electronegative atom (not hydrogen). Carbon and sulfur are common central atoms.
Step 3 — Place single bonds: Connect all surrounding atoms to the central atom with single bonds (2 electrons each).
Step 4 — Complete octets on outer atoms: Add lone pairs to surrounding atoms until each has 8 electrons (2 for H).
Step 5 — Complete the central atom: Place remaining electrons on the central atom as lone pairs.
Step 6 — Form multiple bonds if needed: If the central atom lacks an octet, convert lone pairs on adjacent atoms into double or triple bonds.

Valence Electron Reference

Common atoms: H=1, C=4, N=5, O=6, F=7, Cl=7, S=6, P=5, Si=4, Br=7

Frequently Asked Questions

What is a Lewis dot structure? +

A Lewis dot structure shows the valence electrons of atoms in a molecule as dots, and covalent bonds as lines. It helps predict bonding, molecular shape, and formal charges. Developed by Gilbert N. Lewis in 1916.

How do you count valence electrons? +

Valence electrons equal the group number for main-group elements: Group 1=1, Group 2=2, Groups 13–17=3–7, Group 18=8. For a molecule, sum the valence electrons of all atoms and adjust for any ionic charge (subtract for cation, add for anion).

What is the octet rule? +

The octet rule states atoms tend to form bonds until they have 8 electrons in their valence shell. Hydrogen only needs 2 (duet rule). Some elements like sulfur and phosphorus can have expanded octets (more than 8 electrons) using d-orbitals.

What is formal charge? +

Formal charge = valence electrons − lone pair electrons − (½ × bonding electrons). The best Lewis structure minimizes formal charges (closest to zero) and places negative formal charges on the most electronegative atoms.

What is a lone pair in chemistry? +

Lone pairs (non-bonding pairs) are valence electrons not shared between atoms. They occupy space around the central atom and affect molecular geometry per VSEPR theory. Water (H₂O) has 2 lone pairs on oxygen, giving it a bent shape.

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