Type any molecular formula — CO₂, H₂O, N₂, SO₂, MgCl₂, Br₂ and more — and get a fully worked Lewis diagram with valence electrons, bonding pairs, lone pairs and formal charges calculated in real time.
Built for students, teachers and anyone who wants a fast, accurate lewis diagram generator with real chemistry rules — not guesses.
Valence electrons, bonding pairs and lone pairs are computed live using the actual octet-filling algorithm, not a static image library.
Molecular compounds like CO₂ get shared dot pairs; salts like MgCl₂ automatically switch to a cation / anion charge diagram.
Every atom's formal charge is calculated and flagged, so you can double-check resonance structures and stability at a glance.
The formula field checks capitalisation, element symbols and charge notation as you type, catching typos before you submit.
Copy the structure summary to your clipboard or download the diagram as a PNG for assignments, slides and lab reports.
No page reloads or waiting rooms — the generator solves and draws the structure client-side the moment you submit.
The same four steps a chemistry teacher would use on a whiteboard, applied automatically to your formula.
Every atom's group-number electrons are added together (adjusted for any overall ionic charge you enter).
The least electronegative non-hydrogen atom becomes the skeleton's center; every other atom bonds to it.
Remaining electrons fill outer atoms to a full octet first, then the center, following standard bonding priority.
If the central atom is short, a neighboring lone pair becomes a double or triple bond until every atom is stable.
Enter a chemical formula exactly as written (case sensitive), e.g. H2O, CO2, SO2, MgCl2.
Use standard capitalisation: carbon is C, cobalt is Co, chlorine is Cl.
A Lewis dot structure is a shorthand drawing that chemists use to show how the outermost, or valence, electrons of atoms are arranged when they join to form a molecule or an ion. Instead of memorising each shape from a textbook, a Lewis diagram generator applies the same logic a chemistry student would use by hand: count every valence electron in the formula, work out which atom sits in the middle, share electron pairs to form bonds, and then park whatever is left over as lone pairs until each atom has a full outer shell. That is exactly the process this lewis structure builder runs the moment you press generate, which is why the diagrams you get back match what you would draw on paper or see in a lab manual.
Teachers introduce Lewis structures early in general chemistry because they explain, in one picture, why water bends into an angle, why carbon dioxide is a straight line, and why table salt does not behave like a typical molecule at all. Once you can read a diagram you can predict a molecule's shape, guess whether it will be polar, and reason about how reactive it might be. That is also why so many students search for a lewis diagram generator rather than working every formula out from scratch during an exam review session — the tool does the electron bookkeeping instantly and lets you focus on understanding the shape and the chemistry behind it.
Start by adding up the valence electrons contributed by every atom in the formula, remembering to add one electron for each negative charge or subtract one for each positive charge if you are drawing an ion. Next, choose the least electronegative atom that is not hydrogen as the centre of the molecule, since hydrogen can never take more than one bond. Connect every remaining atom to that centre with a single bond, which uses up two electrons per connection. Whatever electrons remain are placed on the outer atoms first, filling each one to eight electrons, and any leftover pairs go on the central atom. Finally, check whether the central atom has a full octet; if it does not, move a lone pair from a neighbouring atom into the bond to create a double or triple bond, repeating until every atom is satisfied.
The lewis dot structure of CO2 is one of the clearest examples of this process in action: carbon sits in the centre with sixteen total valence electrons to place, and because a single bond to each oxygen leaves carbon two electrons short of an octet, both connections become double bonds, giving oxygen two lone pairs each and carbon none. Water works differently — with eight valence electrons total, oxygen keeps two lone pairs after forming single bonds to both hydrogens, which is also why the molecule bends into its familiar shape rather than staying straight. Nitrogen gas, written N2, only has two atoms to work with, so all ten valence electrons go into a triple bond between the nitrogens plus one lone pair on each side, explaining why the N2 triple bond is so difficult to break.
Sulfur dioxide is a slightly trickier case: sulfur is the centre of the lewis dot structure of SO2, and because sulfur can hold more than eight electrons, the real molecule is best described as a resonance hybrid with one double bond and one single bond to the two oxygens, plus a lone pair sitting on sulfur itself. Bromine, on the other hand, only ever appears as Br2, a simple diatomic molecule where two bromine atoms share a single bond and each keeps three lone pairs to complete its own octet. Compounds like the lewis dot structure of MgCl2 are different again, because magnesium and chlorine are not sharing electrons at all — magnesium gives up both of its valence electrons to become a 2+ ion, while each chlorine atom accepts one electron to become a 1− ion with a full set of four lone pairs, so the "structure" is really a pair of separate ions rather than a covalently bonded molecule.
| Formula | Name | Bond type | Central atom |
|---|---|---|---|
| H2O | Water | Covalent, bent | Oxygen |
| CO2 | Carbon dioxide | Covalent, linear (double bonds) | Carbon |
| N2 | Nitrogen gas | Covalent, triple bond | — |
| SO2 | Sulfur dioxide | Covalent, bent (resonance) | Sulfur |
| MgCl2 | Magnesium chloride | Ionic | — |
| Br2 | Bromine | Covalent, single bond | — |
Type formulas with correct capitalisation, since "co" and "Co" mean carbon monoxide and cobalt respectively, and this lewis structure builder relies on that distinction to identify each element correctly. For ions, use the charge field rather than typing a plus or minus sign into the formula itself, and remember that very large or unusual formulas outside common general-chemistry coursework may not have a single definitive structure, in which case the tool will flag the result as approximate. With practice, most students find that comparing a hand-drawn attempt against the generator's output is one of the fastest ways to catch small mistakes, like forgetting a lone pair or miscounting valence electrons, before a quiz or lab report is due.
Add up every atom's valence electrons, choose the least electronegative non-hydrogen atom as the centre, connect all other atoms to it with single bonds, fill outer atoms to a full octet with the remaining electrons, place any leftovers on the centre, and convert an outer lone pair into a double or triple bond if the centre still needs more electrons.
Carbon dioxide's structure has carbon in the middle double-bonded to each oxygen atom, giving every atom eight electrons overall — two lone pairs on each oxygen and none on carbon — in a straight, linear arrangement.
Magnesium chloride is ionic, not covalent, so the diagram shows a magnesium ion with a 2+ charge and no dots, alongside two separate chloride ions, each in brackets with four lone pairs and a 1− charge, rather than shared bonding pairs.
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