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प्रश्न
Explain the following term with suitable examples:
Frenkel defect
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उत्तर
This defect arises when an ion (generally a cation) leaves its lattice site and occupies an interstitial site.
The void or empty space between the lattice points is known as an interstitial site. Fig. depicts a Frenkel flaw. It is evident from the image that instead of having its own proper location in the lattice, one of the A+ ions occupies a spot in the interstitial space. As seen in the illustration, this results in a hole being made in the lattice. Because the number of positive ions equals the number of negative ions, the crystal is nonetheless neutral despite this defect, maintaining the compound’s stoichiometry and electrical neutrality.
Frenkel flaws do not impact the crystal’s density. They conduct electricity in crystals and cause diffusion in solids. The presence of Ag+ ions in the interstitial region of AgBr crystals creates photographic images when exposed to light. Frenkel flaws raise the dielectric constant of crystals. Frenkel flaws cause charges to move closer within the crystal.
Frenkel defects are common in silver halides, e.g., AgCl, AgBr and Agl. They are also found in ZnS crystals.
संबंधित प्रश्न
Explain the following term with a suitable example:
Interstitials
What type of defect is shown by NaCl in
stoichiometric defects, and
Out of NaCl and AgCl, which one shows Frenkel defect and why?
Dislocation defect is also known as ____________.
The radius of Cs+ is 169 pm and Cl− is 181 pm. The radius ratio is ____________.
Which is not correct about the Schottky defects?
Assertion: Due to Frenkel defect, there is no effect on the density of the crystalline solid.
Reason: In Frenkel defect, no cation or anion leaves the crystal.
Which of the following crystals does not exhibit Frenkel defect?
What is the effect of Frenkel defect on the density of ionic solids?
Cations are present in the interstitial sites in ______.
Schottky defect is observed in crystals when ______.
Which of the following defects is also known as dislocation defect?
Which of the following statements are not true?
(i) Vacancy defect results in a decrease in the density of the substance.
(ii) Interstitial defects results in an increase in the density of the substance.
(iii) Impurity defect has no effect on the density of the substance.
(iv) Frankel defect results in an increase in the density of the substance.
Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R):
Assertion: In any ionic solid (MX) with Schottky defects, the number of positive and negative ions are same.
Reason: Equal number of cation and anion vacancies are present.
Given below are two statements:
Statements I: Frenkel defects are vacancy as well as interstitial defects.
Statements II: Frenkel defect leads of colour in ionic solids due to the presence of F-centers.
Choose the most appropriate answer for the statements from the options given below:
