Which of the following defects exhibit colour to solid alkali metal halides?

Step-by-step solution

Solid alkali metal halides such as NaCl , LiCl , and KCl exhibit characteristic colors due to a type of non-stoichiometric defect called a metal excess defect. When crystals of NaCl are heated in an atmosphere of sodium vapor, sodium atoms deposit on the crystal surface. Chloride ions ( Cl⁻ ) diffuse to the surface and combine with sodium atoms to form NaCl . During this reaction, sodium atoms lose electrons to form Na⁺ ions. The released electrons diffuse into the crystal lattice and occupy the vacant anionic site