Explain the defects arising due to anionic vacancies and due to the presence of extra cations in the interstitial sites.

Use the appropriate symbols $T$ (True) or $F$ (False) for the following statements regarding defects in solids:
$(1)$ Frenkel defect arises due to the arrangement of cations and anions with a very small difference in size.
$(2)$ Frenkel defect can be called a dislocation defect.
$(3)$ $F$-centers arise due to the migration of electrons released from metal atoms into the crystal lattice.
$(4)$ Physical properties of the crystal do not change due to Schottky defect.

Which among the following solids shows Frenkel defect?

Which is the incorrect statement?

Schottky defect generally appears in

Which of the following is $NOT$ a characteristic of Schottky defect?