Which one among the following does not have an allotrope?

Allotropy is the property of some chemical elements to exist in two or more different physical forms in the same state [1]. Carbon exhibits extensive allotropy, with forms including diamond, graphite, and fullerenes [1]. Sulphur is highly versatile, existing in various allotropic forms such as rhombic (orthorhombic) and monoclinic sulphur. Oxygen also possesses allotropes, specifically dioxygen (O2) and ozone (O3). While nitrogen can form complex structures like polymeric nitrogen under extreme laboratory conditions, it is generally considered in standard chemistry curricula not to exhibit allotropy in the same manner as carbon, sulphur, or oxygen. In the context of general science and competitive examinations like UPSC, nitrogen is the element among the choices that does not have commonly recognized allotropic forms, whereas the others are classic examples of the phenomenon.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Table 3.1 > p. 40