$A$ 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.

$A$ binary compound $(A^{+} B^{-})$ has a rock salt structure. If the edge length is $400 \, pm$ and the radius of the cation $(A^{+})$ is $75 \, pm$, what is the radius of the anion $(B^{-})$ in $pm$?

Gold has a face-centered cubic $(fcc)$ lattice with an edge length of the unit cube of $407 \, pm$. The diameter of the gold atom is .............. $pm$.

Calculate the radius of an atom of an element in $pm$ if it forms $bcc$ unit cell structure having edge length $4.3 \times 10^{-8} \ cm$.

The density of $NaCl$ is $2.165 \, g \, cm^{-3}$. The distance between $Na^+$ and $Cl^-$ ions in the $NaCl$ crystal is $281 \, pm$. Based on this information,the value of Avogadro's number is ...

Iron exhibits $bcc$ structure at room temperature. Above $500^{\circ} C$,it transforms to $fcc$ structure. Find the ratio of the density of iron at room temperature to that at $500^{\circ} C$. (Assume the atomic radii and the molar mass of iron remain constant even with variation in temperature)