(i) What type of non-stoichiometric point defect is responsible for the pink colour of LiCl?
(ii) What type of stoichiometric defect is shown by NaCl?

OR

How will you distinguish between the following pairs of terms:
(i) Tetrahedral and octahedral voids
(ii) Crystal lattice and unit cell

(i) The reason for pink colour of LiCl is Metal excess defect due to anionic vacancies filled by free electrons or we can say that it is due to F – centres.

(ii) NaCl shows Schottky defect as there is a very small difference between the ionic radii of Na⁺ and Cl^-.

OR

(i) Tetrahedral void is the void surrounded by 4 constituent particles and it has the shape of a regular tetrahedron while Octahedral void is the void surrounded by 6 constituent particles and an octahedron is formed by them.

The coordination no. of tetrahedral voids and octahedral voids are 4 and 6 respectively.

(ii) Unit cell is the smallest portion of a lattice which is used to describe a lattice while the lattice formed by the repetition of unit cell in three dimensions is called a crystal lattice.