What is the atomic radius of polonium if it crystallises in a simple cubic structure with edge length of unit cell $336 \ pm$ (in $pm$)?

Gold (atomic radius $= 0.144 \, nm$) crystallises in a face-centred unit cell. What is the length of a side of the cell?

Niobium crystallizes in a $bcc$ structure. If its density is $8.55 \, g/cm^3$, calculate the atomic radius of niobium. [Atomic mass of $Nb = 93 \, u$] (in $pm$)

$X$-rays of wavelength $1 \ \mathring{A}$ are diffracted by the planes of particles in a metal. The second-order diffraction occurs at an angle of $60^{\circ}$. Calculate the distance between two parallel planes in $\mathring{A}$.

An element occurs in the body-centred cubic $(BCC)$ structure with an edge length of $288 \ pm$. The density of the element is $7.2 \ g \ cm^{-3}$. The number of atoms present in $208 \ g$ of the element is nearly:

$A$ metal crystallises in a face-centred cubic $(FCC)$ structure with a metallic radius of $\sqrt{2} \ \mathring{A}$. The volume of the unit cell (in $m^{3}$) is: