Which of the following is not a characteristic of a crystalline solid?

The correct answer is Option (2) → Isotropic nature

A crystalline solid has its particles in a regular arrangement that repeats throughout the crystal (long range order). Its physical properties, such as electrical resistance or refractive index, differ along different directions: crystalline solids are anisotropic. Amorphous solids, with only short range order, are isotropic.

• Option (1) Definite and characteristic heat of fusion — A characteristic of a crystalline solid. Every particle is held in the same way, so the crystal melts sharply at a fixed temperature with a definite heat of fusion.

• Option (2) Isotropic nature — Not a characteristic of a crystalline solid. Crystalline solids are anisotropic; isotropy belongs to amorphous solids such as glass and rubber.

• Option (3) A regular periodically repeated pattern of arrangement of constituent particles in the entire crystal. — A characteristic of a crystalline solid. This is its long range order.

• Option (4) True solid. — A characteristic of a crystalline solid. Crystalline solids are called true solids; amorphous solids are pseudo solids (supercooled liquids).

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):
Crystalline and Amorphous Solids – “… Crystalline solids are anisotropic in nature, that is, some of their physical properties like electrical resistance or refractive index show different values when measured along different directions in the same crystals.”

Crystalline and Amorphous Solids – “… Amorphous solids on the other hand are isotropic in nature. It is because there is no long range order in them and arrangement is irregular along all the directions.”