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 $pm$?

The distance between two nearest $Ag$ atoms is $2.5 \times 10^{-8} \ cm$. The density of its crystal is .......... $g/cm^3$. $(Ag = 108 \ g/mol)$

Copper crystallises in a $ccp$ arrangement and the accepted value of the metal ion radius was found to be $1.28 \ \mathring{A}$. Calculate the density of copper in grams per cubic centimetre. (Atomic weight of copper is $63.5 \ g/mol$,$N_A = 6.022 \times 10^{23} \ mol^{-1}$) (in $g/cm^3$)

Lithium has a $bcc$ structure. Its density is $530 \ kg \ m^{-3}$ and its atomic mass is $6.94 \ g \ mol^{-1}$. Calculate the edge length of a unit cell of lithium metal in $pm$ $(N_A = 6.02 \times 10^{23} \ mol^{-1})$.

How many unit cells are present in a cube-shaped ideal crystal of $NaCl$ of mass $1.00 \ g$? [Atomic masses: $Na = 23, Cl = 35.5$]

Calculate the interplanar spacing between the $111$ planes in a $Ca$ crystal (in $nm$). Given that the edge length of the $Ca$ unit cell is $0.556 \ nm$.