Teacher explained the stoichiometric defects in a class room. a) Explain with the help of diagrams the important differences in Schottky and Frenkel defects. by What are the consequences? (b) Illustrate the above law by using a chemical reaction.
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Answer:
consequencesimportant differences in Schottky and Frenkel defects. by What are the consequences
i) Schottky defect
Some atoms or ions are missing from their normal lattice sites. Unoccupied lattice sites are called vacancies or holes.
For example, in the crystal lattice of NaCl, equal number of cations and anions are missing to maintain electrical neutrality.
(ii) Frenkel defect
An ion is missing from its normal position and occupies an interstitial site.
Due to this, vacancy defect and interstitial defect are produced.
For example, in the crystal lattice of ZnS, a zinc cation is missing from its normal position and occupies an interstitial site.
(iii) Interstitials
They are sites between lattice points.
For example, in Frenkel defect, the occupancy of interstitials cause interstitial defect.
(iv) F-centres
The electrons trapped in anion vacancies are called F-centres. They impart colour to crystal.
For example, in NaCl crystal, F-centres impart yellow colour