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

Experimentally,it was found that a metal oxide has the formula $M_{0.98}O$. The metal $M$ is present as $M^{2+}$ and $M^{3+}$ in its oxide. The fraction of the metal which exists as $M^{3+}$ would be: .................... $\%$

Which defect leads to an increase in the density of a solid?

Assertion : Due to Frenkel defect,there is no effect on the density of the crystalline solid.
Reason : In Frenkel defect,no cation or anion leaves the crystal.

In the $AgBr$ crystal,the size of ions follows the order $Ag^{+} << Br^{-}$. Which of the following characteristics is shown by $AgBr$?

As a result of Schottky defect,the density of the crystal: