Which of the following is not a property of \(\alpha\)-sulphur?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → It has monoclinic structure
Sulphur has two common crystalline allotropes: rhombic sulphur (α-sulphur) and monoclinic sulphur (β-sulphur). The yellow colour, the melting point 385.8 K and the solubility in \( \ce{CS2} \) belong to the rhombic form; the monoclinic structure is that of β-sulphur.
Option (1) It is readily soluble in \(CS_2\) — A property of α-sulphur. Rhombic sulphur dissolves readily in \( \ce{CS2} \); its crystals are obtained by evaporating this solution.
Option (2) It has monoclinic structure — Not a property of α-sulphur (a property of β-sulphur). α-Sulphur is rhombic; the monoclinic form is β-sulphur, stable above 369 K.
Option (3) This allotrope is yellow in colour — A property of α-sulphur. Rhombic sulphur is yellow.
Option (4) Its melting point is \(385.8 K\) — A property of α-sulphur. 385.8 K is the melting point of rhombic sulphur; monoclinic sulphur melts at 393 K.
Note: 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):
Sulphur – Allotropic Forms
