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 $g \ cm^{-3}$)

Sodium metal crystallizes in a $bcc$ lattice with a unit cell edge length of $a = 4.29 \ \mathring{A}$. What is the radius of the sodium atom in $\mathring{A}$?

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 $NaCl = 58.5 \ g \ mol^{-1}$)

When silver crystallizes, it forms face-centered cubic $(FCC)$ unit cells. If the volume of the unit cell is $6.84 \times 10^{-23} \text{ cm}^3$, calculate the density of silver. (Molar mass of silver is $108 \text{ g/mol}$, $N_A = 6.022 \times 10^{23} \text{ mol}^{-1}$) (in $\text{ g cm}^{-3}$)

Ammonium chloride crystallizes in a body-centered cubic lattice with an edge length of the unit cell of $390 \ pm$. If the size of the chloride ion is $180 \ pm$,the size of the ammonium ion would be ........... $pm$.

What are the variables in the graph of powder diffraction pattern of a crystalline solid?