Match List I with List II
| List I | List II |
| A. Hexagonal | I. \(\alpha ≠ \beta ≠ \gamma ≠ 90^o\) |
| B. Orthorhombic | II. \(\alpha = \gamma = 90^o; \beta ≠ 90^o\) |
| C. Triclinic | III. \(\alpha = \beta = 90^o; \gamma = 120^o\) |
| D. Monoclinic | IV. \(\alpha = \beta = \gamma = 90^o\) |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → A-III, B-IV, C-I, D-II
The seven crystal systems differ in their axial distances (a, b, c) and axial angles (α, β, γ):
Cubic: a = b = c; α = β = γ = 90°
Tetragonal: a = b ≠ c; α = β = γ = 90°
Orthorhombic: a ≠ b ≠ c; α = β = γ = 90°
Hexagonal: a = b ≠ c; α = β = 90°, γ = 120°
Rhombohedral: a = b = c; α = β = γ ≠ 90°
Monoclinic: a ≠ b ≠ c; α = γ = 90°, β ≠ 90°
Triclinic: a ≠ b ≠ c; α ≠ β ≠ γ ≠ 90°
(A) Hexagonal — This matches (III) α = β = 90°, γ = 120°. It is the only system with a 120° angle.
(B) Orthorhombic — This matches (IV) α = β = γ = 90°. All three angles are right angles; only the three edges differ.
(C) Triclinic — This matches (I) α ≠ β ≠ γ ≠ 90°. It is the least symmetrical system: no angle is 90°.
(D) Monoclinic — This matches (II) α = γ = 90°, β ≠ 90°. Only one angle departs from 90°.
Shortcut: (A)-(III) appears in Options (1) and (4); (B)-(IV) then leaves only 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.