Polonium (atomic mass = $209$) crystallises in a simple cubic structure with a density of $9.32 \ g \ cm^{-3}$. Its lattice parameter (in $pm$) is closest to:

The second order Bragg's diffraction of $X$-rays with $\lambda = 1 \ \mathring{A}$ from a set of parallel planes in a metal occurs at an angle of $60^\circ$. The distance between the scattering planes in the crystal is ................ $\mathring{A}$.

Metal $M$ crystallizes into a $FCC$ lattice with the edge length of $4.0 \times 10^{-8} \ cm$. The atomic mass of the metal is $........ \ g/mol$. (Nearest integer). (Use: $N_{A} = 6.02 \times 10^{23} \ mol^{-1}$,density of metal,$d = 9.03 \ g \ cm^{-3}$)

An ionic compound $X^{+}Y^{-}$ has a $bcc$ structure. The distance between two nearest ions is $1.73 \, \mathring{A}$. What would be the edge length of the unit cell in $pm$?

In a face-centered cubic $(FCC)$ unit cell, if the edge length is $508 \text{ pm}$, what is the radius of the atom in $\text{pm}$?

Calculate the number of unit cells in $0.79 \ g$ of a metal if the product of the density and the volume of the unit cell is $1.58 \times 10^{-22} \ g$.