The edge length of a face centered cubic cell of an ionic substance is $508 \, pm.$ If the radius of the cation is $110 \, pm,$ the radius of the anion is ........... $pm$.

Iron oxide $FeO$ crystallises in a cubic lattice with a unit cell edge length of $5.0 \ \mathring{A}$. If the density of the $FeO$ in the crystal is $4.0 \ g \ cm^{-3}$,then the number of $FeO$ units present per unit cell is $...........$ (Nearest integer).
Given: Molar mass of $Fe$ and $O$ is $56$ and $16 \ g \ mol^{-1}$ respectively.
$N_{A} = 6.0 \times 10^{23} \ mol^{-1}$

$Cu$ metal crystallizes in an $fcc$ or $ccp$ lattice. If the edge length of its unit cell is $361 \ pm$, what is the radius of the $Cu$ atom (in $pm$)?

Calculate the volume of the unit cell of an element having a molar mass of $27 \ g \ mol^{-1}$ that forms an $fcc$ unit cell. Given: $\rho \cdot N_{A} = 16.0 \times 10^{23} \ g \ cm^{-3} \ mol^{-1}$.

Which formula is used to calculate edge length $(a)$ in a $bcc$ structure,where $r$ is the radius of the atom?

$A$ metal crystallizes in two cubic phases,$fcc$ and $bcc$,whose unit cell edge lengths are $3.5 \ \mathring{A}$ and $3.0 \ \mathring{A}$ respectively. Calculate the ratio of the densities of $fcc$ and $bcc$ phases.