Which one of the following elements does not exhibit allotropic modification?

Allotropy is the property of an element to exist in two or more different structural forms with distinct physical properties but similar chemical properties [t3][t5]. Carbon exhibits well-known allotropes such as diamond, graphite, and fullerenes [c1][c4][t6]. Sulphur exists in several allotropic forms, including rhombic, monoclinic, and amorphous varieties [t10]. Phosphorus also exhibits allotropy, commonly found as white, red, and black phosphorus [t7][t10]. In contrast, halogens generally do not show this type of allotropic property [t1]. While iodine is a lustrous non-metal [c1], it does not exhibit allotropic modification in the same manner as carbon, sulphur, or phosphorus. Although some sources discuss high-pressure phases of iodine, in the context of standard chemical principles and the provided evidence, it is the element among the choices that does not exhibit traditional allotropy [t1].

Sources

1. [1] https://www.matanginicollege.ac.in/studyMaterial/125720Chemistry%20of%20s%20and%20p%20block%20element.pdf
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Table 3.1 > p. 40
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > Allotropes of carbon > p. 61
4. [4] https://www.cec-ugc.nic.in/webpath/curriculum/Module/APPIC/Paper07/5/downloads/script.pdf