Question

Discuss the following property and its variation in the group 15 elements:

Allotropy

Answer 1

1. Allotropy refers to the existence of an element in more than one physical form in the same physical state.
2. In group 15, allotropy is mainly observed in phosphorus and arsenic.
3. Phosphorus shows allotropy in forms like white phosphorus (P₄ tetrahedral molecules), red phosphorus (polymeric network), and black phosphorus (layered structure).
4. Arsenic also shows allotropy, with grey arsenic being a metallic layered structure and yellow arsenic resembling white phosphorus.
5. Nitrogen, antimony, and bismuth do not exhibit significant allotropy.
6. Variation in allotropy down the group depends on atomic size and bonding; lighter elements form molecular allotropes, and heavier ones form metallic or network structures.
7. The allotropes vary in stability, bonding type, and physical properties due to differences in atomic arrangements.