Q 1.21:Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.

Q 1.21:Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.

Solution:

When a cation of higher valence is added as impurity  in an  ionic solid . two or more than two cations of lower valances is replace by less than 2 ions of higher valances . To maintain the electrical neutrality few sites become vacant,

For example,

Sr²⁺ is added to NaCl, each Sr2+ ion replaces two Na⁺ ions. Because the charge on 1 ions of Sr²⁺ is equal to charge on two ions of Na+. and One Na⁺ ions leave there