Sodium metal crystallizes in $B.C.C.$ lattice with an edge length of $4.29 \ \mathring{A}$. The radius of the sodium atom is:

The correct relationship between unit cell edge length '$a$' and radius of sphere '$r$' for face-centred and body-centred cubic structures respectively are:

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 $4.0 \, g \, cm^{-3}$,the number of $Fe^{2+}$ and $O^{2-}$ ions present in each unit cell will be ($M_w$ of $FeO = 72$)

In a face-centered cubic $(FCC)$ unit cell, if the edge length is $508 \text{ pm}$, what is the radius of the atom in $\text{pm}$?

Calculate the density of an element with molar mass $27 \ g \ mol^{-1}$ having $4$ atoms in a unit cell with edge length $405 \ pm$. (in $g \ cm^{-3}$)

Fill in the blanks:
$1.$ Density of unit cell $(d) = ........$
$2.$ Mass of atoms present in unit cell $(m) = ........$