$A$ binary compound $(A^{+} B^{-})$ has a rock salt structure. If the edge length is $400 \, pm$ and the radius of the cation $(A^{+})$ is $75 \, pm$, what is the radius of the anion $(B^{-})$ in $pm$?

The distance between $Na^{+}$ and $Cl^{-}$ ions in solid $NaCl$ of density $2.165 \ g \ cm^{-3}$ is $........ \times 10^{-10} \ m$. (Nearest Integer)
(Given : $N_{A} = 6.02 \times 10^{23} \ mol^{-1}$,Molar mass of $NaCl = 58.5 \ g \ mol^{-1}$)

An ionic solid $X^{+} Y^{-}$ crystallizes in a $bcc$ structure. If the distance of the closest approach between the two ions is $173 \ pm$, what is the edge length of the unit cell in $pm$?

$A$ metal (atomic mass $= 50$) has a body-centered cubic $(bcc)$ crystal structure. If the density of the metal is $5.96 \, g \, cm^{-3}$,then the volume of the unit cell is ............ $\times 10^{-24} \, cm^3$.

Niobium crystallizes in a $bcc$ structure. If its density is $8.55 \, g/cm^3$, calculate the atomic radius of niobium. [Atomic mass of $Nb = 93 \, u$] (in $pm$)

An element $M$ crystallises in a body-centred cubic unit cell with a cell edge of $300 \, pm$. The density of the element is $6.0 \, g \, cm^{-3}$. The number of atoms present in $180 \, g$ of the element is $............ \times 10^{23}$ (Nearest integer).