2.7 - How to determine main structure if formal charges are equal?

[nicolely2F]

Exercise 2.7 asks to draw all the resonance structures for the salt (a chain structure) and to indicate the most important structure (where there aren't any two like charges side-by-side). I drew the three structures, but all three structures have 2 N-atoms with FC = +1 and 1 N-atom with FC = -1. In this case, how do I determine the structure of lowest energy?

[Daria Azizad 1K]

Usually, it is best to have differing FC side by side (like a -1 next to +1) rather than the same FC side by side (like +1 next to +1) because it is unlikely that there would be two same charge centers in close proximity due to repulsive forces.

[Amina Durrani 3G]

The lowest energy structure would have the most electronegative N in the middle (-1 FC) and the two other N’s (+1 FC) on either side.