Which structures below are plausible resonance contributors for NCNH⁻? Assume the connectivity is as written.

Question

Which structures below are plausible resonance contributors for NCNH⁻? Assume the connectivity is as written.

https://content.101edu.co/static/images/resonance_ncnh.png

Answer 1

I and III look like plausible resonance contributions for NCNH^-

II doesn't appear correct because of connectivity, and IV doesn't look favorable because of the formal charge distribution on both nitrogen atoms (-2 and +1).