Lewis structure generator

Start typing, and the structure redraws as you go.

• Type a molecular formula such as C2H6O, a name such as ethanol, or a SMILES string.
• If a formula fits several molecules, pick the isomer you mean. C₂H₆O can be ethanol or dimethyl ether.
• Switch between a Lewis and a skeletal formula, and show lone pairs as bars or dots.
• Download a PNG with a transparent background, or put it on a board with your worksheet.

A Lewis structure shows how the valence electrons of a molecule are arranged: the bonding pairs between atoms, drawn as lines, and the lone pairs that belong to one atom. It tells you which atoms are connected and how, which is why it is usually where questions about shape and polarity start.

Take water. Oxygen brings six valence electrons and each hydrogen one, eight in total. Two pairs form the O–H bonds, and the remaining four electrons sit on the oxygen as two lone pairs, giving it a full octet.

Common school molecules come from a library whose entries are each tested against their formula. Conventions differ between courses, and this tool picks one: acids such as H₂SO₄, H₃PO₄ and HClO₄ use the expanded-octet form with the fewest formal charges, while elements of period 2 never exceed the octet, so nitric acid, ozone and carbon monoxide carry charges.

If your textbook draws one differently, follow your textbook. It also shows a single structure, rather than all the resonance forms of a molecule, so it is worth knowing when your molecule has them.