Sodium metal crystallizes in a body-centred cubic $(bcc)$ lattice with a unit cell edge of $4.29 \ \mathring{A}$. The radius of the sodium atom is approximately ............. $\mathring{A}$.

Calculate the molar mass of an element having density $21 \ g \ cm^{-3}$ that forms $fcc$ unit cell $[a^3 \cdot N_{A} = 36 \ cm^3 \ mol^{-1}]$

Bragg's law is given by the equation

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 $(N_A = 6.0 \times 10^{23} \ mol^{-1})$

What is the number of unit cells present in $3.9 \ g$ of potassium if it crystallizes in $BCC$ structure?

Aluminum crystallizes in a cubic close-packed structure. If its metallic radius is $125 \ pm$, what is the side length of the unit cell?