Chemistry - Solid State Question with Solution | TestHub

When NaCl crystal is doped with ${\text{MgCl}}_2$, ${\text{Mg}}^{2+}$ ions replace ${\text{Na}}^{+}$ ions in the crystal lattice.

To maintain electrical neutrality, one ${\text{Mg}}^{2+}$ ion replaces two ${\text{Na}}^{+}$ ions. One ${\text{Mg}}^{2+}$ ion occupies the site of one ${\text{Na}}^{+}$ ion, leaving the other site vacant, which creates a cation vacancy.

Since a foreign ion is introduced into the host crystal, this type of defect is known as an impurity defect.

Answer: Impurity defect