In $FCC$ lattice,alternate tetrahedral voids are occupied in which of the following?

The radius of a calcium ion is $94 \text{ pm}$ and of the oxide ion is $146 \text{ pm}$. The possible crystal structure of calcium oxide will be

In a mixed oxide of two metals $X$ and $Y$,divalent $X^{2+}$ ions occupy $50\%$ of the tetrahedral voids,while trivalent $Y^{3+}$ ions occupy $50\%$ of the octahedral voids. The formula of the oxide is:

Calculate the coordination number of $Na^{+}$ in $NaCl$ crystal, given the radii of $Na^{+}$ and $Cl^{-}$ are $95 \ pm$ and $181 \ pm$ respectively.

If the edge length of a cubic unit cell in an $fcc$ structure is $620 \ pm$, then the atomic radius of the element will be ............... $pm$.

In a crystal of $NaCl$, the distance between $Na^{+}$ and $Cl^{-}$ is $x \, pm$. What is the edge length of the unit cell?