Question

What type of the following defect is produced when NaCl crystal is doped with \(\text{MgCl}_{2}\)?

• A. Interstitial defect
• B. Schottky defect
• C. Frenkel defect
• D. Impurity defect

Hint:

Mg2+ replaces Na+ ions and creates cation vacancies for charge balance, which is an impurity defect.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
When NaCl is doped with \(\text{MgCl}_{2}\), a \(\text{Mg}^{2+}\) ion takes the place of a \(\text{Na}^{+}\) ion.

Step 2: Charge balance
Since \(\text{Mg}^{2+}\) has twice the charge, one more \(\text{Na}^{+}\) site is left vacant so the crystal stays neutral.

Step 3: Name
A foreign ion entering the lattice makes it an impurity defect, with a cationic vacancy.

Final Answer:
The defect is an impurity defect. \[ \boxed{\text{(D) }\text{Impurity defect}} \]