Which of the following point defects are shown by $AgBr_{(s)}$ crystals?
$A$. Schottky defect
$B$. Frenkel defect
$C$. Metal excess defect
$D$. Metal deficiency defect

In spite of long-range order in the arrangement of particles,why are the crystals usually not perfect?

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:

Due to the Frenkel defect,the density of a solid $..........$

The flame colours of metal ions are due to

Which of the following is non-stoichiometric?