Question

With suitable explanation, give a brief account of the allotropy exhibited by the elements of group 16.

Answer 1

1. All elements of group 16 show allotropy, existing in several allotropic forms.
2. Oxygen exists mainly as dioxygen (O₂) and ozone (O₃), where dioxygen is more stable.
3. Sulphur has many allotropes, mainly:
   1. Homocyclic species with 6-20 atoms, the most stable being orthorhombic S₈.
   2. Catena-S_n sulphur (chain polymers).
   3. Unstable small S_n molecules (n = 2-5) in liquid and vapour states.
4. Selenium shows six allotropes, three red monoclinic types with Se₈ rings and a stable grey hexagonal monoclinic form with infinite spiral chains.
5. Tellurium has two allotropes, metallic and non-metallic.
6. Polonium exists in two metallic allotropes called α and β forms.

Thus, allotropy in group 16 varies from simple diatomic forms to complex ring and chain structures, with stability and structure differing down the group.