Question

Considering formal charge arguments, the most likely Lewis structure for

SCN- has how many double bonds?

Answer 1

The most likely Lewis structure for SCN- has double bond character due to resonance, typically depicted with a single double bond between sulfur and carbon.

Step-by-step explanation:

When determining how many double bonds are present in the most likely Lewis structure for SCN-, considering formal charges is critical. For the thiocyanate ion (SCN-), possible structures include NCS, CNS, and CSN, each with different formal charges for sulfur, carbon, and nitrogen.

The formal charge calculation involves the subtraction of the number of valence electrons in the free atom from the number assigned to it in the Lewis structure. The structure with the smallest sum of absolute formal charge values is typically favored. Regarding SCN-, one of the structures with minimum formal charges includes a triple bond between carbon and nitrogen and a single bond between carbon and sulfur, satisfying the octet rule for all atoms and yielding a formal charge of -1 on the sulfur atom to account for the overall negative charge of the ion.

Therefore, the most likely Lewis structure for SCN- has one double bond between sulfur and carbon when considering resonance forms that distribute the double bond character between the sulfur-carbon and carbon-nitrogen bonds.

Answer 2

The most likely Lewis structure for SCN- with respect to formal charges has sulfur with a single bond and a negative charge, carbon with a triple bond to nitrogen and a single bond to sulfur, resulting in only one double bond.

Step-by-step explanation:

The most likely Lewis structure for the SCN- ion, considering formal charge arguments, would be the one where the sum of the formal charges of the atoms is closest to zero and each atom has a formal charge as close to zero as possible. For the cyanide ion, sulfur usually forms two bonds, carbon forms four bonds, and nitrogen forms three bonds. This could result in a structure where carbon is triple-bonded to nitrogen and single-bonded to sulfur, with sulfur also having a lone pair and a single negative charge to account for the overall negative charge of the ion. Thus, this structure tends to have only one double bond between carbon and sulfur, as additional double bonds would increase the formal charges on the atoms.