In an ionic crystal,$F$-centers are.....

Missing of one monovalent cation and one monovalent anion from the crystal lattice is called

Zinc oxide (white) is heated to high temperature for some time. Observe the following statements regarding the above process:
$I$. Zinc oxide colour changes to pale yellow
$II$. The type of defect formed is 'metal deficiency'
$III$. Some $Zn^{2+}$ and $e^{-}$ are present in interstitial places
The correct statements are:

What is a point defect?

Stoichiometric defects are also called ........................ .

If molten $NaCl$ contains $SrCl_2$ as impurity,crystallization can generate