The formal charge is the "charge" an element would have in a molecule or ion if all of the bonding electrons were shared equally between atoms We can draw three inequivalent Lewis structures for the cyanate ion , OCN. The concepts of formal charge and electronegativity can help us choose the structure that is the best representation. 1. Assign formal charges to the elements in each of the structures below OC N: :03 - N: O C Formal Charge 2. The best Lewis structure for OCN is z