How many unit cells share a corner of a unit cell in a crystal lattice?

Percentage of free space in a body-centred cubic unit cell is ................ $\%$

What is the percentage of empty space in a $bcc$ unit cell (in $\%$)?

If $0.5 \ mol$ of a metal forms a hexagonal close-packed structure,the total number of voids and tetrahedral voids respectively in $mol$ are

In a close-packed structure of mixed oxides,the lattice is composed of oxide ions. One-eighth of the tetrahedral voids are occupied by divalent cations $(A^{2+})$,while one-half of the octahedral voids are occupied by trivalent cations $(B^{3+})$. The formula of the mixed oxide is:

$A$ compound formed by $Mg$,$Al$,and $O$ is found to have a cubic close-packed $(CCP)$ array of oxide ions,in which $Mg^{2+}$ ions occupy $\frac{1}{8}^{th}$ of the tetrahedral voids and $Al^{3+}$ ions occupy $\frac{1}{2}$ of the octahedral voids. The formula for the compound is: