Calculate the coordination number of $Na^{+}$ in $NaCl$ crystal, given the radii of $Na^{+}$ and $Cl^{-}$ are $95 \ pm$ and $181 \ pm$ respectively.

$A$ certain metal crystallizes in a $bcc$ lattice. The distance between the nearest neighbours is $433 \text{ pm}$. The distance between the next nearest neighbours is :- .............. $\text{pm}$

In a face-centered cubic lattice of $X$ and $Y$ atoms,$X$ atoms are present at the corners while $Y$ atoms are at the face centers. If two atoms of $X$ are missing from the corners,what is the formula of the compound?

In a mineral $MX_2$,$M^{+2}$ ions are arranged in a $ccp$ structure and $X^{-}$ ions occupy the tetrahedral voids. What are the number of cations and anions per unit cell,the coordination number of the cation,and the percentage of occupied tetrahedral voids,respectively?

Calculate the total number of atoms in a $bcc$ crystal lattice containing $2 \times 10^{23}$ unit cells.

Number of atoms per unit cell for body centered cubic system is