Question:
When crystals of sodium chloride are heated in the presence of sodium vapour, they turn yellow. This is due to the formation of:
When crystals of sodium chloride are heated in the presence of sodium vapour, they turn yellow. This is due to the formation of:
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Excess metal defect: an electron trapped in an anion vacancy produces colour.
Updated On: Jul 3, 2026
- Schottky defects
- Frenkel defects
- F-centres
- H-centres
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The Correct Option is C
Solution and Explanation
Step 1: Excess Na atoms deposit and ionize to Na+, occupying cation sites.
Step 2: Released electrons get trapped in anion vacancies.
Step 3: This trapped-electron vacancy is called F-centre.
Step 4: Trapped electrons absorb visible light, giving yellow colour.
\[\boxed{\text{F-centres}}\]Was this answer helpful?
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