At $T \ K$, copper (atomic mass $= 63.5 \ u$) has $fcc$ structure with an edge length of $x \ \mathring{A}$. The density of copper (in $g \ cm^{-3}$) at that temperature is approximately $(N_A = 6.0 \times 10^{23} \ mol^{-1})$

An element has a crystalline structure where the unit cell is a cube with one atom at each corner and two atoms on its body diagonal. If the volume of this unit cell is $24 \times 10^{-24} \, cm^3$ and the density of the element is $7.2 \, g \, cm^{-3}$,then the number of atoms present in $200 \, g$ of the element is:

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 .............. $pm$.

$X$-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 $\mathring{A}$.

The correct relationship between unit cell edge length '$a$' and radius of sphere '$r$' for face-centred and body-centred cubic structures respectively are:

$A$ compound can crystallise in two forms $\alpha$ and $\beta$ which are $fcc$ and $bcc$, respectively. The $\alpha$-form has a side length of $2 \ pm$ and the $\beta$-form has a side length of $4 \ pm$. The ratio of their density $\frac{\rho_\alpha}{\rho_\beta}$ is