Question

What type of crystal defect is produced when sodium chloride is doped with MgCl₂?

Explain the nature of crystal defect produced when sodium chloride is doped with magnesium chloride.

Answer 1

1. When sodium chloride (NaCl) is doped with magnesium chloride (MgCl₂), it introduces a type of non-stoichiometric defect called a cation vacancy defect.
2. In this process, some of the Na⁺ ions in the NaCl crystal are replaced by Mg²⁺ ions. Since the Mg²⁺ ion has a +2 charge, it substitutes for two Na⁺ ions to maintain electrical neutrality.
3. One Mg²⁺ ion occupies one Na⁺ site, and the other Na⁺ site is left vacant, creating a cation vacancy.
4. This defect helps in maintaining the overall charge balance of the crystal and is classified as a non-stoichiometric impurity defect.