A Lewis dot structure shows all valence electrons in a molecule — bonding pairs as lines between atoms, and lone pairs as dots on individual atoms. They are the foundation of predicting molecular geometry, polarity, and chemical reactivity using VSEPR theory.
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Common Molecules
Lewis Structure
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How to Use the Lewis Structure Generator
Lewis dot structures are the foundation of understanding chemical bonding. The Lewis structure generator visualizes valence electron distribution for 28+ common molecules using the SmilesDrawer library for accurate 2D rendering.
Step 1: Select or Type a Molecule
Click any molecule in the quick-select grid (H₂O, CO₂, NH₃, etc.) or type a molecular formula in the text box. For ions, include the charge: SO4^2-, NO3-, NH4+. Then click "Draw Lewis Structure."
Step 2: Read the Structural Diagram
The canvas shows the 2D Lewis structure rendered from SMILES notation. Single lines represent single bonds (one shared electron pair), double lines represent double bonds (two pairs), and triple lines represent triple bonds (three pairs). For water (H₂O), the bent structure shows two O–H single bonds with two lone pairs on oxygen. For carbon dioxide (CO₂), two C=O double bonds appear with lone pairs on each oxygen.
Step 3: Check Electron Statistics
Below the diagram, the tool shows: total valence electrons in the molecule, number of bonding pairs (each bond = one bonding pair), total lone pairs, and formal charge. For molecules with non-zero formal charges like O₃ (ozone) or NO₃⁻ (nitrate), the formal charges are broken down per atom in an amber callout.
Understanding Resonance Structures
Several molecules in the database have resonance structures — multiple valid Lewis structures that contribute to the actual bonding. Ozone (O₃), benzene (C₆H₆), nitrate (NO₃⁻), carbonate (CO₃²⁻), and sulfate (SO₄²⁻) all exhibit resonance. The generator renders one canonical resonance form, and the indigo callout explains the resonance concept for that molecule.
Hypervalent Molecules
The database includes hypervalent molecules that expand beyond the octet rule: SF₆ (12 electrons around sulfur), PCl₅ (10 electrons around phosphorus), IF₅ (12 electrons around iodine), and XeF₂ (10 electrons around xenon). These are only possible for elements in period 3 and beyond that can use d orbitals for bonding.
FAQ
Is the Lewis Structure Generator free?
Yes, completely free. No signup, no download, and no account required. All rendering runs in your browser using the SmilesDrawer library.
Is my data private?
Yes. All calculations and structure rendering happen locally in your browser. No data is sent to any server.
What is a Lewis dot structure?
A Lewis dot structure (or electron dot structure) shows all valence electrons in a molecule — bonding pairs shared between atoms appear as lines, while non-bonding lone pairs appear as dots. They are fundamental to predicting molecular geometry and reactivity.
How do I count valence electrons for a Lewis structure?
Sum up the valence electrons for each atom in the molecule (group number for main-group elements). For ions, add electrons for negative charge or subtract for positive charge. Then distribute electrons to satisfy the octet rule for each atom (duet for hydrogen).
What are formal charges in Lewis structures?
Formal charge = (valence electrons of neutral atom) - (lone pair electrons) - (1/2 × bonding electrons). The best Lewis structure minimizes formal charges and places negative charges on the most electronegative atoms.
What are resonance structures?
Some molecules like ozone (O3), benzene (C6H6), and nitrate (NO3-) cannot be described by a single Lewis structure. Resonance structures are two or more valid Lewis structures for the same molecule — the real structure is a hybrid blend of all resonance forms.
Can this tool draw hypervalent molecules like SF6 and PCl5?
Yes. The database includes hypervalent molecules that violate the octet rule (SF6, PCl5, IF5, XeF2) using expanded octets with d-orbital participation. These are included with proper SMILES notation for accurate SmilesDrawer rendering.