According to valence bond theory, the oscillating nature of double bonds in benzene is now proposed by resonance. Double bonds keep on changing their positions. The structures produced are such that the position of nucleus remains the same in each structure. The structure formula of such a compound is somewhat intermediate between various proposed formulae. This state is known as resonance. The hybrid structure is represented by inserting a circle or a dotted line as in figure C. The circle represents six electrons delocalized between six carbon atoms of benzene ring.

Catenation can be defined as the self-linking of atoms of an element to form chains and rings. This definition can be extended to include the formation of layers like two-dimensional catenation and space lattices like three-dimensional catenation. The most common examples of catenation or elements that exhibit catenation are: Carbon, Silicon, Sulphur, Boron. Catenation occurs most readily in carbon, forming covalent bonds to form longer chains and structures with other carbon atoms. This is why the vast number of organic compounds are found in nature. Carbon is best known for its catenation properties, with the analysis of catenated carbon structures in organic chemistry. All the elements of carbon family or group 4 family exhibit catenation property. The first member from the family has the highest tendency to catenate. Following is the tendency to catenate: C > Si > Ge > Sn > Pb Catenation tendency decreases down the group. This happens because the atomic size increases down the group and the strength of the covalent bond decreases. Hence, the catenation property decreases down the group.