Which member of 15 group elements does not show allotropy?

Nitrogen

The correct answer is Option (1) → Nitrogen

Allotropy is the existence of an element in different physical forms in the same state. Most Group 15 elements show allotropy, except nitrogen.

Option 1: Nitrogen - Exists as diatomic molecule (N₂) with strong triple bond. Does not form different structural forms. Hence, does not show allotropy.

Option 2: Phosphorus - Shows several allotropes like: • White phosphorus • Red phosphorus • Black phosphorus Hence, shows allotropy.

Option 3: Arsenic - Exists as: • Yellow arsenic • Grey arsenic • Black arsenic Hence, shows allotropy.

Option 4: Antimony-  Exists in: • Metallic form • Non-metallic form Hence, shows allotropy.