Among the following solids,Schottky defect is $NOT$ observed in-

Ionic solids,which have anionic vacancies due to metal excess defect,develop colour. Explain with the help of a suitable example.

Which type of crystal defect is observed in the diagram given below?
$Na^{+} Cl^{-} Na^{+} Cl^{-} Na^{+} Cl^{-}$
$Cl^{-} \square Cl^{-} Na^{+} \square Na^{+}$
$Na^{+} Cl^{-} \square Cl^{-} Na^{+} Cl^{-}$
$Cl^{-} Na^{+} Cl^{-} Na^{+} \square Na^{+}$

Schottky defect in crystals is observed when

Identify the defect developed when an ion of an ionic compound is missing from its regular site and occupies an interstitial position between lattice points.

In a solid lattice,the cation has left a lattice site and is located at an interstitial position. The lattice defect is: