Given below are two statements.
Statement I: Frenkel defects are vacancy as well as interstitial defects.
Statement II: Frenkel defect leads to colour in ionic solids due to presence of F-centres.
Choose the most appropriate answer for the statements from the options given below:
Statement I: Frenkel defects are vacancy as well as interstitial defects.
Statement II: Frenkel defect leads to colour in ionic solids due to presence of F-centres.
Choose the most appropriate answer for the statements from the options given below:
- (A)Both Statement I and Statement II are true
- (B)Statement I is false but Statement II is true
- (C)Both Statement I and Statement II are false
- (D)Statement I is true but Statement II is false✓ Correct
Answer: (D)
Solution
A Frenkel defect forms when an ion, usually the smaller cation, leaves its lattice site and lodges in an interstitial hole, so one and the same defect produces a vacancy and an interstitial together; Statement I is true. Colour from an F-centre arises when an anion vacancy traps an electron, which happens in a metal excess defect; a Frenkel defect only relocates an ion within the crystal and leaves no anion vacancy and no trapped electron, so it does not produce F-centres. Statement II is false, so Statement I is true but Statement II is false.
JEE Main · 2021 · 26 Aug 2021 · Shift 1 · Single correct option