Question

Match the types of defects given in column I with the statement given in column II

Column I	Column II
A. Impurity Defect	1. NaCl with anionic sites called F-centres
B. Metal Excess Defect	2. FeO with \[{\rm{F}}{{\rm{e}}^{{\rm{3 + }}}}\]
C. Metal deficiency defect	3. NaCl with \[{\rm{S}}{{\rm{r}}^{{\rm{2 + }}}}\] and some cationic sites vacant

Answer 1

Hint: In a solid, different types of defect occur due to the difference in the arrangement of constituent particles. In a solid, if the arrangement of solids becomes distorted around a point is termed a point defect.

Complete Step by Step Answer:
The impurity defect is due to the replacement of some of the atoms of the solid by some foreign atom. And for maintaining electrical neutrality, there will be some vacant cationic sites. For example, in NaCl molecule, one \[{\rm{S}}{{\rm{r}}^{{\rm{2 + }}}}\]ion replaces an sodium ion and to maintain neutrality, one sodium ion becomes vacant. So, option A matches with option 3.

Let's understand metal excess defects. In this type of defect, anions are replaced by electrons termed F-centres. And this causes more metal atoms (cations) than the anions. For example, NaCl molecules having anionic sites called F centres. Therefore, option B matches with option 1.

Now we will discuss metal deficiency defects. This defect occurs because of the variable valence state of the metal where some cations are missed from their lattice sites. And for maintaining electrical neutrality, another cation possessing higher valency is introduced. For example, FeO crystal has \[{\rm{F}}{{\rm{e}}^{{\rm{3 + }}}}\]ion. Therefore, option C matches with option 2.

Therefore, correct matches are,

Column I	Column II
A. Impurity Defect	3. NaCl with \[{\rm{S}}{{\rm{r}}^{{\rm{2 + }}}}\] and some cationic sites vacant
B. Metal Excess Defect	1. NaCl with anionic sites called F-centres
C. Metal deficiency defect	2. FeO with \[{\rm{F}}{{\rm{e}}^{{\rm{3 + }}}}\]

Note: There are two other types of defect namely Frenkel and Schottky defect. In ionic solids, the Frenkel defect is seen in ionic solids where smaller ions (cations) are dislocated such as in AgBr, AgCl etc. Schottky defect is observed in potassium chloride, sodium chloride.