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 an electron in an excited atom jumps from the $L$ shell to the $K$ shell,$X$-rays are emitted. These $X$-rays undergo first-order diffraction at an angle of $7.75^{\circ}$ by a crystal with an interplanar spacing of $2.64 \ \mathring{A}$. Calculate the energy difference between the $K$ shell and the $L$ shell. $(\sin \ 7.75^{\circ} = 0.1349)$

Sodium crystallizes in $bcc$ structure with radius $1.86 \times 10^{-8} \text{ cm}$. What is the edge length of unit cell of sodium?

An element crystallises in an $fcc$ unit cell with a cell edge length of $3.608 \times 10^{-8} \text{ cm}$. The density of the element is $8.92 \text{ g cm}^{-3}$. Calculate the atomic mass of the element $(N_A = 6.022 \times 10^{23} \text{ mol}^{-1})$. (in $\text{ g/mol}$)

The substance $CuCl$ has a $ZnS$ $(ccp)$ structure. If its density is $3.4 \ g \ cm^{-3}$, what is the edge length of the unit cell?

$A$ metal has a $fcc$ lattice. The edge length of the unit cell is $404 \, pm$. The density of the metal is $2.72 \, g \, cm^{-3}$. The molar mass of the metal is ................. $g \, mol^{-1}$.
($N_A$ Avogadro's constant $= 6.02 \times 10^{23} \, mol^{-1}$)