Question

Kcl crystal is colourless . But on heating it in an atmosphere of pottasium vapour it become violet in colour . Account for this

Answer 1

Answer:

Due to the presence of F-centres

Explanation:

When KCl is heated with small amount of K, at first the K atoms lose one electron and forms K+ ions. Again some of the Cl- from the lattice sites moves towards the surface creating some holes inside. The negative electrons from the surface occupy the emplty anionic sites which are called F-centres. Due to these F centres it imparts colour