Question

What is the resonance structure for ${C_6}{H_6}$?

Answer 1

Hint: The given compound is Benzene, which is a 6-carbon ring structure with the presence of alternate double bonds between carbon atoms. Resonance structure would be all the possible bond positions between the atoms.

Complete answer:
The electrons and bonds of a molecule can be visualised using Lewis dot structures. However, several molecules have several contributing or "resonance" structures since not all bonding possibilities can be described by a single Lewis structure. The idea that electrons are delocalized, or move freely through the molecule, allows for several structures to be possible for a given molecule, and this is known as resonance.
However, it is important to remember that none of these structures can be observed in nature. That is, the molecule does not necessarily switch back and forth between these configurations; rather, the true structure is a close approximation of each of them. This intermediate, known as a resonance hybrid, has a lower total energy than any of the possible configurations.
We know that the benzene molecules have cyclic structure with alternating single and double bonds between adjacent carbon atoms. A hydrogen atom is bonded to every carbon atom. According to valence bond theory, the oscillating double bonds in the benzene ring are explained using resonance structures. The benzene ring's carbon atoms are all $s{p^2}$ hybridised. Six C-C sigma bonds are formed when one of one atom's two $s{p^2}$ hybridised orbitals overlap with the $s{p^2}$ orbital of an adjacent carbon atom. Six C-H sigma bonds are formed when other left $s{p^2}$ hybridised orbitals combine with hydrogen s orbital. By lateral overlap, the remaining unhybridized p orbitals of carbon atoms form bonds with neighboring carbon atoms. This explains why C1 – C2, C3 – C4, C5 – C6 bonds or C2 – C3, C4 – C5, C6-C1 bonds are equally likely to form.
This explains the two possible benzene resonance structures which are shown below. In the figure below, a circle is inserted into the ring to represent the hybrid structure.

Note:
It's important to remember that the difference between each of these resonance structures is determined by the position of the electrons and not by the atoms' arrangement. Actually, the benzene molecule is stabilized by resonance as the pi electrons are delocalized around the ring structure. In this structure each carbon-carbon bond has a bond order of 1.5 as a result of the delocalization, meaning that they are stronger than normal C-C sigma bonds.