key questions 1. what distinguishes each of the four examples in illustrating the methodology? 2. why might it be necessary to put double or even triple bonds between atoms in constructing lewis structures? 3. how does the lewis structure help you identify the length of bonds in a molecule? 4. how is formal charge determined, and how is it used in identifying reasonable lewis structures? 5. in the above examples illustrating the methodology, why are relevant resonant structures - present only in the case of no2 ?