Calculate the molar mass of an element if it forms fcc unit cell structure [mass of unit cell $=1.8 \times 10^{-22} \mathrm{~g}, \mathrm{~N}_{\mathrm{A}}=6.022 \times 10^{23} \mathrm{~mol}^{-1}$ ]

The volume of simple unit cell is $x \times 10^{-23} \mathrm{~cm}^3$. Calculate the value of $x$ if volume occupied by a particle in it is $2.1 \times 10^{-23} \mathrm{~cm}^3$.

In ionic solid, anions are arranged in ccp array and cations occupy $1 / 3$ tetrahedral voids. What is the formula of ionic compound?

[Consider $\mathrm{A}=$ cation; $\mathrm{B}=$ anion]

Which of the following statements is NOT correct regarding voids in lattice structure?