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

Calculate the molar mass of an element having density $5.6 \ g \ cm^{-3}$ that forms a $bcc$ structure. $\left[a^3 \times N_{A}=75 \ cm^3 \ mol^{-1}\right]$

What is the relationship between the edge length $(a)$ and the radius of the atom $(r)$ in a simple cubic unit cell?

An element crystallises in $bcc$ type crystal structure with an edge length of unit cell $300 \ pm$. Calculate the radius of the element.

$KBr$ has a rock salt type structure and has a density of $3.70 \ g/cm^3$. The edge length of the unit cell is approximately [molecular weight of $KBr = 120 \ g/mol$]:

Ferrous oxide has a cubic structure and each edge of the unit cell is $5.0 \ \mathring{A}$. Assuming the density of the oxide is $4.0 \ g \ cm^{-3}$,calculate the number of $Fe^{2+}$ and $O^{2-}$ ions present in each unit cell ($M_w$ of $FeO = 72 \ g/mol$).