Match List-I with List-II
List-I | List-II |
(A) Cubic cell | (I) \(\alpha = \beta = \gamma = 90^o\) |
(B) Monoclinic cell | (II) \(\alpha = \beta = 90^o, \gamma = 120^o\) |
(C) Triclinic cell | (III) \(\alpha = \gamma = 90^o, \beta \ne 90^o\) |
(D) Hexagonal cell | (IV) \(\alpha \ne \beta \ne \gamma \ne 90^o\) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-I, B-III, C-IV, D-II
The seven crystal systems differ in their unit-cell parameters: the edge lengths a, b, c and the angles α, β, γ between the edges. The angles alone are enough to tell these four systems apart.
(A) Cubic cell — This matches (I) α = β = γ = 90°. All three angles are right angles (and a = b = c).
(B) Monoclinic cell — This matches (III) α = γ = 90°, β ≠ 90°. Only one angle, β, differs from 90° (a ≠ b ≠ c).
(C) Triclinic cell — This matches (IV) α ≠ β ≠ γ ≠ 90°. It is the least symmetrical system: no two angles equal, none 90° (a ≠ b ≠ c).
(D) Hexagonal cell — This matches (II) α = β = 90°, γ = 120°. The base is a rhombus with a 120° angle (a = b ≠ c).
Shortcut: the 120° angle belongs only to the hexagonal system (D-II); only Options (3) and (4) have it, and A-I (cubic, all 90°) leaves Option (4).
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.