Calculate the number of unit cells in $1 \ cm^3$ of an element if the unit cell edge length is $2.0 \times 10^{-8} \ cm$.

Calculate the distance between two parallel $(220)$ planes in a crystal with an edge length of $450 \, pm$. (in $pm$)

The density of $Na$ is $0.613 \ g \ cm^{-3}$. If the edge length of the unit cell of $Na$ is $5 \ \mathring{A}$,the effective number of atoms of $Na$ per unit cell is (Atomic weight of $Na = 23 \ u$)

What is the relation between edge length $a$ and the total volume occupied by atoms in a $BCC$ unit cell?

An element has a $bcc$ structure with a cell edge of $288 \ pm$. The density of the element is $7.2 \ g \ cm^{-3}$. What is the atomic mass of the element?

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. $(\sin \ 7.75^{\circ} = 0.1349)$