Which defect causes a decrease in the density of a crystal?

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.

Alkali halides do not show dislocation defect because

What is a point defect?

Assertion : No compound has both Schottky and Frenkel defects.
Reason : Both defects change the density of the solid.

Due to $Frenkel$ defect,the density of ionic solids