Sodium metal crystallizes in a body-centred cubic $(bcc)$ lattice with a unit cell edge of $4.29 \ \mathring{A}$. The radius of the sodium atom is approximately ............. $\mathring{A}$.

For a $Cr$ crystal crystallizing in a $bcc$ structure, the edge length of the unit cell is $287 \, pm$. What is the density of the crystal in $\text{g/cm}^3$? $(Cr = 51.99 \, \text{g/mol})$

$A$ solid having density of $9 \times 10^3 \ kg \ m^{-3}$ forms face-centred cubic crystals of edge length $200 \sqrt{2} \ pm$. What is the molar mass of the solid? [Avogadro constant $\cong 6 \times 10^{23} \ mol^{-1}$,$\pi \cong 3$]

$A$ substance forms a face-centered cubic $(FCC)$ crystal. Its density is $1.984 \ g \ cm^{-3}$ and the edge length of the unit cell is $630 \ pm$. Calculate the molar mass of the substance in $g \ mol^{-1}$.

Identify the instrument used to determine the crystal structure from the following:

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 $pm$ $(N_A = 6.02 \times 10^{23} \ mol^{-1})$.