Count total valence electrons for all atoms (sum group numbers; add electrons for anions; subtract for cations)
Choose the central atom (least electronegative atom; hydrogen never central)
Connect atoms with single bonds first (each bond = 2 electrons); write skeleton structure
Distribute remaining electrons to satisfy the octet (or duet for H) on outer atoms using lone pairs
Check each outer atom’s valence:
If an atom has fewer than an octet, form multiple bonds by converting lone pairs into bonding pairs between atoms
Ensure the central atom satisfies octet (allow expanded octets for period 3+ elements when needed)
Add lone pairs to the central atom if electrons remain after octet completion
Verify total electron count matches the original total valence electrons
Assign formal charges to each atom:
Formal charge = (valence electrons) − (nonbonding electrons) − (bonding electrons/2)
Select the most plausible structure:
Minimize formal charges
Negative formal charge on more electronegative atoms
Prefer octets over expanded octets when possible
For resonance structures:
Produce all valid structures with the same total valence electrons and octet rules
Use the one with best formal-charge criteria (or note multiple equivalent resonances)
Final check:
All atoms have correct valence satisfaction (octet/duet as appropriate)
Total formal charges sum to the overall ion charge
All electrons are accounted for and bonds/lone pairs are consistent