In a crystal,Frenkel defect is observed only when the radius ratio is......

Identify the incorrect statement regarding crystals having $Frenkel$ defect.

Metal deficiency defect is shown by $Fe_{0.93}O$. In the crystal,some $Fe^{2+}$ cations are missing and loss of positive charge is compensated by the presence of $Fe^{3+}$ ions. The percentage of $Fe^{2+}$ ions in the $Fe_{0.93}O$ crystals is $....$ (Nearest integer)

Which one of the following crystals does not exhibit Frenkel defect?

The defect that arises when smaller cations move into interstitial sites in a crystal lattice is known as ..............

$NaCl$ is heated in an atmosphere of sodium vapour. The resultant yellow colour is due to the formation of