Question

Schottky defect in a crystal is observed when

• A. The ion leaves its normal position and occupies an interstitial location
• B. The unequal number of cation and anions are missing from the lattice
• C. The density of the crystal increases.
• D. An equal number of cations and anions are missing from the lattice.

Hint:

Schottky defects create vacancies in a crystal by removing equal numbers of cations and anions, leading to a decrease in density.

Answer 1

The Correct Option is D

Step 1: Understanding Schottky Defect
A Schottky defect occurs in a crystal when equal numbers of cations and anions are missing from the lattice sites, creating vacancies.
This type of defect maintains the overall electrical neutrality of the crystal.
Step 2: Explanation of Other Options
Option (a) describes an interstitial defect, where an ion occupies an interstitial space, which is not a Schottky defect.

Option (b) is incorrect because a Schottky defect involves equal numbers of cations and anions being missing, not unequal numbers.
Option (c) is incorrect because the density of the crystal decreases due to the vacancies created in Schottky defects.

Step 3: Conclusion Thus, a Schottky defect in a crystal occurs when an equal number of cations and anions are missing from the lattice.