Geo-Scientist Prelims 2022 Chemistry Q24: Which one of the following is not a resonance structure of…

Which one of the following is not a resonance structure of thiocyanate (SCN⁻)?

1. (a) :S̈=C=N̈:⁻ (S=C double, C=N double, formal charge −1 on N)
2. (b) :S̈:⁻—C≡N: (S–C single, C≡N triple, formal charge −1 on S)
3. (c) :S⁺≡C—N̈:²⁻ (S≡C triple, C–N single, +1 on S and −2 on N)
4. (d) S²⁻—C=N̈:⁻ (S–C single, C=N double, −2 on S and −1 on N)