Lewis Structure Builder

• Click a palette atom to drop it on the board, then drag it into place.

• Drag one unpaired electron onto another atom's unpaired electron to form a bond (shown as a line with blue "spent" electron pairs). Repeat between the same two atoms for double/triple bonds.

• Drag one unpaired electron onto another unpaired electron on the same atom to pair them into a lone pair.

• Drag a lone pair onto another atom to form a dative (coordinate) bond - both electrons come from the source, so this works even if the target has no electrons of its own. That's how you build ions like NH4+ or H3O+: reduce an H down to 0 electrons with the "-" button, then drag a lone pair onto it.

• Click a lone pair (without dragging) to split it back into two unpaired electrons.

• Use the small +/- buttons on each atom to add or remove an electron, for building ions (e.g. Cl to Cl-, or H to a bare H+).

• Click a bond line to remove one bond order.

• Hover a formal charge badge to see how it was calculated.

• A pulsing red ring means the atom still has unpaired electron(s) sitting loose - that's a radical, not a finished lone pair. Formal charge can still read 0 for a radical, since charge and octet completeness are different things - the ring is what actually tells you the atom isn't done.