What is the mass of a $bcc$ type unit cell of sodium if the mass of one atom of sodium is $3.819 \times 10^{-23} \ g$?

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

$A$ compound is formed by elements $A$ and $B$. Element $A$ occupies the corners of the cube,and element $B$ occupies the face centers. What is the formula of the compound?

Calculate the volume of a unit cell having an atomic radius of $141.4 \ pm$ forming an $fcc$ unit cell.

Potassium crystallizes in a $bcc$ lattice,hence the coordination number of potassium in potassium metal is

In a compound formed by $A^{+}$ and $B^{-}$ ions,$B^{-}$ ions are arranged at all corners except two and at all face centers except three,while $A^{+}$ ions are at the midpoints of all body diagonals. The molecular formula of the compound will be ................