Question

How are crystals classified?

(a) According to the place of origin

(b) According to the position of the unit cells

(c) According to the symmetry of the unit cells

(d) According to the purity of the unit cells

This question was addressed to me in a national level competition.

This question is from Crystal Geometry topic in section Crystallization of Food Processing Unit Operations

Answer 1

Right answer is (c) According to the symmetry of the unit cells

Easy explanation: The crystals structures are classified according to the symmetry of the unit cells. There are in 7 groups, collectively called Crystal Systems, they are monoclinic, tricinic, orthorhombic, tetragonal, trigonal, cubic and hexagonal.