Question

Which of the following is NOT true for solid crystals?

• A. Definite and characteristic heat of fusion
• B. Isotropic nature
• C. A regular periodically repeated pattern of arrangement of constituent particles in the entire crystal
• D. A true solid

Answer 1

The correct option is B

Isotropic nature

Explanation for correct option

(B) Isotropic nature

Crystalline Solid

• Crystalline solids have their atoms, ions, or molecules organized in a definite, repeating pattern.
• Every atom or molecule of the same type is held in place by the same forces or energy.
• Crystalline solids have exact melting points.
• Crystalline solids are anisotropic in nature.
• A crystal or crystalline solid is a true solid.

Isotropic nature

• When measured in several directions, isotropic substances have the same value for physical properties like electrical conductivity and refractive index, exactly like glass or liquid.
• Amorphous substances exhibit Isotropy.

Explanation for incorrect options

(A) Definite and characteristic heat of fusion

• Every atom or molecule of the same type is held in place by the same forces or energy in crystalline solids
• Therefore they have definite and characteristic heat of fusion.

(C) A regular, periodically repeated pattern of arrangement of constituent particles in the entire crystal

• Crystalline solids have their atoms, ions, or molecules organized in a definite, repeating pattern.

(D) A true solid

• A crystalline solid is a true solid.
• They have a regular arrangement of particles.

Therefore the correct option is (B) Isotropic nature.