Thiocyanate Lewis Structure [ENDORSED]

[Olivia_Chen_3E]

In 4.8 of the organic chemistry textbook, it asks to draw two lewis structures for SCN-. In the solutions, the negative sign for the two different lewis structures is on either the S or the N molecule, and I was wondering why this was, and if it had anything to do with thiocyanate being an ambident nucleophile, and how the lone pairs impacted this.

[Chem_Mod]

If it's just asking for the Lewis structures of the ion, then the charge is most likely to be on the nitrogen or sulfur atom because they're more electronegative. An ambident nucleophile is one in which the charge is delocalized via. resonance, which is the case of the thiocyanate ion.

[Sunny Chera 1N]

When constructing the lewis structure of Azide, N3-, I noticed that the solution put a positive charge on the central nitrogen atom and negative charges on the outer nitrogen atoms. I do not understand why the central nitrogen atom would have a positive charge on it? Since they are all nitrogen atoms, wouldn't they all have the same electronegativities? I am suspecting that this might be the case because azide is an ambident nucleophile due to the lone pairs on the two outer nitrogen atoms and the overall delocalization?

[Navarro_Bree_1D]

The central N atom has 4 electrons than its usual 5. That's why there is a positive charge on it