If the number of atoms in a unit cell is $2$,then the number of tetrahedral and octahedral voids will be ....... and ....... respectively.

When sodium is heated above $1000 \ K$,its crystal structure changes from $bcc$ to $fcc$. Assuming the metallic radius of the atom remains unchanged,the ratio of the fraction of volume occupied by atoms in $bcc$ and $fcc$ structures will be .......

In a solid $AB_2$,the coordination number of $A$ is $8$. It has a cubic close-packed $(ccp)$ lattice. Half of the $B$ atoms are,however,ejected from the solid. Now,the number of tetrahedral holes (voids) that remain filled is:

$A$ metal forms an $fcc$ structure. Calculate the volume of the $fcc$ unit cell in $\text{cm}^3$ if the void volume is $1.66 \times 10^{-23} \text{ cm}^3$.

$A$ metal crystallizes in a lattice having $AB AB AB$ sequence of layers. This arrangement of spheres corresponds to which type of packing,and what is the percentage of empty space (void volume) in this lattice?

In a $ccp$ structure of a mixed oxide,$1/8$ of the tetrahedral voids are occupied by divalent $X^{+2}$ ions and $50\%$ of the octahedral voids are occupied by trivalent $Y^{+3}$ ions. The formula of the oxide is: