In an ionic solid,equal number of cations and anions are missing from their regular positions in the crystal lattice,creating vacancies. This is called-

When $Fe_{0.93}O$ is heated in the presence of oxygen,it converts to $Fe_2O_3$. The number of correct statement$(s)$ from the following is:
$A.$ The equivalent weight of $Fe_{0.93}O$ is $\frac{\text{Molecular weight}}{0.79}$.
$B.$ The number of moles of $Fe^{2+}$ and $Fe^{3+}$ in $1 \text{ mole}$ of $Fe_{0.93}O$ is $0.79$ and $0.14$ respectively.
$C.$ $Fe_{0.93}O$ is metal deficient with a lattice comprising of a cubic closed-packed arrangement of $O^{2-}$ ions.
$D.$ The $\%$ composition of $Fe^{2+}$ and $Fe^{3+}$ in $Fe_{0.93}O$ is $85\%$ and $15\%$ respectively.

Electron-deficient impurities are caused by the elements of which group?

The pyknometric density of sodium chloride crystal is $2.165 \times 10^3 \ kg \ m^{-3}$ while its $X$-ray density is $2.178 \times 10^3 \ kg \ m^{-3}$. The fraction of unoccupied sites in sodium chloride crystal is

If $10^{-4} \% SrCl_2$ is added to a crystal of $NaCl$,find the number of cationic vacancies created in the crystal.

Identify the defect that develops when the ratio of number of cations to anions becomes different from that indicated by its chemical formula.