Question

Describe the properties of O, S, Se, Te and Po (group 16 elements) with reference to catenation.

Answer 1

The group’s first member, oxygen, shows very little catenation tendency. For example it links its tWo atoms in peroxides, viz., \[\ce{H - O - O - H}\], \[\ce{[- O - O]^{2-}}\], etc.

Sulphur shows a greater tendency towards catenation and links up several atoms in chains. For example, chains of sulphur atoms are present in polysulphides \[\ce{(S^{2-}_n)}\], sulphanes \[\ce{(H - S_n - H)}\], polysulphuric acid \[\ce{(HO3S - S_n - SO3H)}\] and in different allotropic forms of the element. 

Several proteins and enzymes include the \[\ce{S-S}\] bond, which is crucial to biological systems. From S to Po, the catenation tendency significantly diminishes as one moves down the group.