Question

Identify the major and minor resonance contributor(s) for the azide anion, N3-.

??

Answer 1

First of all, some of those resonance structures are incorrect. The sum of formal charges must equal the charge on the ion (or zero for a neutral molecule). Thus D and E are incorrect.

As for major and minor, I would say C is major and A and B are minor. This is because A and B concentrate too much charge on one N atom (-2 versus a maximum charge* of -1 in C).

Another thing to look (although we don't see it here) is whether the structures obey the octet rule. Structures that don't obey the octet rule are usually** minor resonance structures.

*in an absolute value sense

** there are some exceptions, like BF3 where the boron has only 6 electrons in the major resonance structure