Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.
When a cation of better valence is introduced to an ionic strong as an impurity to it, the cation of better valence replaces a couple of cation of decrease valence on the way to hold the crystal electrically neutral. As a result, a few webweb sites become vacant. For example, whilst Sr 2 is brought to NaCl, every Sr 2 ion replaces Na ions. However, one Sr 2 ion occupies the web website online of 1 Na ion and the alternative web website online stays vacant. Hence, vacancies are introduced.
