In a body-centred cubic $(bcc)$ lattice of potassium, the correct relation between the atomic radius $(r)$ of potassium and the edge-length $(a)$ of the cube is:

$A$ 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

An element is found to crystallize with $BCC$ structure having density $8.55 \ g \ cm^{-3}$. What is the edge length of the unit cell? (Atomic mass of element $= 93$)

Which of the following instruments is used to determine the crystal structure?

An element crystallising in $fcc$ lattice has a density of $8.92 \ g \ cm^{-3}$ and edge length of $3.61 \times 10^{-8} \ cm$. What is the atomic weight of the element (in $u$)? $(N_A = 6.022 \times 10^{23} \ mol^{-1})$

What is the atomic mass of an element with $BCC$ structure and density $10 \ g \ cm^{-3}$ having an edge length of $300 \ pm$?