Question

If you include structures in which sulfur has an expanded octet and exclude structures with triple bonds, how many resonance structures can be drawn for sulfur trioxide, SO3.

Answer 1

Concepts and reason

The given question is based on resonating structures of ${\rm{HCO}}_2^ -$ and ${\rm{S}}{{\rm{O}}_3}$ . The stability of resonating structures is based on various factors which are mentioned in the solution.

Fundamentals

When one single structure of a species is not able to explain the bonding and other characteristic properties then resonance comes into picture. It is the delocalization of loosely bound electrons (Pi electrons) with in the given Lewis structure. The structures representing this delocalization is termed as resonating structures.

The formal charge on each atom is calculated and shown as follows:

The provided structures are as follows:

Among these structures only 1 and 4 are valid.

The resonating structures having only double bonds are as follows:

A)When only one double bond is present

B)When two double bonds are present

C)When three double bonds are present

Ans:

The valid and invalid structures are shown below:

The number of possible structures for ${\rm{S}}{{\rm{O}}_3}$ are 7.