Ammonium chloride crystallizes in a body-centered cubic $(BCC)$ lattice with a unit cell edge length of $390 \ pm$. If the radius of the chloride ion is $180 \ pm$, what is the radius of the ammonium ion in $pm$?

$CsBr$ has $b.c.c.$ structure with edge length $4.3 \ \mathring{A}$. The shortest inter-ionic distance between $Cs^{+}$ and $Br^{-}$ is ........... $\mathring{A}$.

Gold crystallises in $fcc$ lattice. The edge length of the unit cell is $4 \ \mathring{A}$. The closest distance between gold atoms is '$x$' $\mathring{A}$ and density of gold is '$y$' $g \ cm^{-3}$. What are $x$ and $y$ respectively?
$($ Molar mass of gold $= 197 \ g \ mol^{-1} ; N_A = 6 \times 10^{23} \ mol^{-1} )$

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:

Calculate the mass of a $bcc$ unit cell if the metal has a molar mass of $56 \ g \ mol^{-1}$.

An element has a $bcc$ structure with an atomic mass of $50$. If the edge length of the unit cell is $290 \ pm$, calculate the density of the unit cell in $\text{g/cm}^{-3}$.