Question

Regarding symmetry of simple cubical lattice which of the following is/are correct ?

• A. It has total 23 symmetry elements
• B. It contain 13 proper rotation axes of symmetry
• C. It contain 9 plane of symmetry
• D. All of the given are correct

Answer 1

Answer: (D)

All of the given are correct

Answer 2

There are three rotation axes are present in a cubic crystal. These are — (i) Tetrad axes (3) (ii) Triad axes (4) (iii) Diad axes (6)

Tetrad axes:- There are three such axes each passing through the centre of the two opposite faces.

Triad axes :- There are four such axes, each passing through the opposite cross corners of the cube.

Diad axes :- There are six such axes, each passing through the centre of two opposite edges of two opposite faces. There are two types of planes in a cubic crystal.

(i) Parallel plane – There are three such planes, each passing through the middle of the two opposite faces and being parallel to the side of the cube.

(ii) Diagonal planes- There are six such planes, each passing through the diagonals of the two opposite faces. There is one centre of symmetry.