What is the Lewis structure of N2O?
Well, we got 16 valence electrons....
16 valence electrons:
...to distribute over 3 centres. And you must simply KNOW here that the oxygen is terminal. And given the example, there will be formal charge separation.
This is half the story inasmuch as we consider the data: i.e. the bond-length of dinitrogen, dioxygen, and nitrous oxide...