Which of the following elements does not show allotropy?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Nitrogen
Allotropy is the existence of an element in two or more forms with different physical properties. All the elements of group 15 except nitrogen show allotropy. Nitrogen exists only as the diatomic \( \ce{N2} \) molecule, held by a very strong triple bond (N≡N), because the small nitrogen atom forms strong pπ–pπ multiple bonds with itself.
Option (1) Nitrogen — Does not show allotropy. It exists only as N2.
Option (2) Bismuth — Shows allotropy.
Option (3) Arsenic — Shows allotropy.
Option (4) Antimony — Shows allotropy.
Note 1: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Physical Properties
Note 2: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | 19-07 S1 | 28-05 S1 | – |