Three nonequivalent Lewis structures are possible for the thiocyanate ion, SCN⁻:
(i) S–C≡N⁻
(ii) S=C=N⁻
(iii) ⁻S≡C–N
Which structure contributes most to the resonance hybrid of SCN⁻? Give one brief justification based on both formal-charge distribution and relative electronegativity of the atoms.