Lewis Structures
Drag atoms from the tray onto the workspace, then click two unpaired electrons to pair them into a bond or lone pair. Right-click a pair to undo it.
Common Questions
How do you draw a Lewis structure step by step?
Count total valence electrons (adjust for charge). Place the least electronegative atom in the center. Connect all atoms with single bonds. Distribute remaining electrons as lone pairs on outer atoms first, then the center. If the central atom lacks an octet, convert lone pairs to double or triple bonds.
What is the octet rule and what are its exceptions?
Most atoms need 8 electrons (shared + lone pairs) to be stable. Exceptions: hydrogen needs only 2; boron and beryllium can have fewer than 8 (incomplete octet); elements in period 3+ (P, S, Cl) can exceed 8 (expanded octet).
How do you choose the central atom in a Lewis structure?
The central atom is usually the least electronegative atom. Hydrogen and fluorine are never central atoms. Carbon is almost always central when present. If multiple candidates exist, the atom that can form the most bonds is typically central.
When do you need double or triple bonds?
When there aren't enough electrons to give every atom an octet using only single bonds and lone pairs. Move a lone pair from an outer atom to form a double bond with the central atom. Repeat for triple bonds if needed.