Name: AB Type Ionic Crystals
Uploaded: 2019-07-19
Duration: 7 min 12 s
Description: Ionic crystals are crystalline structures that grow from ionic bonds and are held together by electrostatic attraction. Let's explore some of the common ionic crystals.

Question

State the difference between Schottky and Frenkel defect. Which of these two changes the density of the solid?

Accepted Answer

In Schottky defect, a pair of vacancies or holes exist in the crystal lattice due to the absence of an equal number of cations and anions from their lattice points. It results in decrease in density of a crystal.
This type of defect is shown by highly ionic compounds which have
(i) High coordination number and
(ii) A small difference in the sizes of cations and anions

Frenkel defect arises due to missing of an ion from its normal position which occupies an interstitial site between the lattice points of the crystal. Due to smaller size, the missing ion is generally cation leaving a hole behind its actual position. There is no net loss of ions from the crystal lattice, so there is no change in the densities in such crystals.

This type of defect is shown by highly ionic compounds which have low coordination number, and anions are much larger than the cations.

State the difference between Schottky and Frenkel defect. Which of these two changes the density of the solid?

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