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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
Out of NaCl and AgCl, which one shows Frenkel defect and why?
Defect shown by non-ionic solids is ____________.
Frenkel defects are not found in alkali metal halides because ____________.
The following diagram shows:
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.
Alkali halids do not show Frenkel defect because ____________.
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 ______.
Frenkel defect is also known as:
(i) stoichiometric defect
(ii) dislocation defect
(iii) impurity defect
(iv) non-stoichiometric defect
Which of the following defects decrease the density?
(i) Interstitial defect
(ii) Vacancy defect
(iii) Frankel defect
(iv) Schottky defect
Why is FeO (s) not formed in stoichiometric composition?
Match the defects given in Column I with the statements in given Column II.
| Column I | Column II |
| (i) Simple vacancy defect | (a) shown by non-ionic solids and increases density of the solid. |
| (ii) Simple interstitial defect | (b) shown by ionic solids and decreases density of the solid. |
| (iii) Frenkel defect | (c) shown by non ionic solids and density of the solid decreases. |
| (iv) Schottky defect | (d) shown by ionic solids and density of the solid remains the same. |
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:
Which type of ‘defect’ has the presence of cations in the interstitial sites?
