Which of the following is most likely the structure of the thiocyanate ion (SCN^-)?

• A. N=C=S^-
• B. S=C=N^-
• C. S-N=C^-
• D. C=S=N^-

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the problem involves determining the most likely Lewis structure of the thiocyanate ion (SCN⁻), which requires considering formal charges and resonance structures.
2. Step 2: Draw possible Lewis structures for SCN⁻, placing the atoms in different orders (e.g., N=C=S⁻, S=C=N⁻, S-N=C⁻, C=S=N⁻) and distributing electrons to satisfy the octet rule as much as possible.
3. Step 3: Calculate the formal charges for each atom in each structure using the formula: \(\text{Formal charge} = \text{Valence electrons} - \text{Nonbonding electrons} - \frac{1}{2} \times \text{Bonding electrons}\).
4. Step 4: Compare the formal charges in each structure, favoring the one where formal charges are minimized and negative charges reside on the more electronegative atoms (S and N are more electronegative than C).
5. Step 5: Identify the structure with the lowest overall formal charge and proper placement of negative charge as the most likely structure of the thiocyanate ion.