Atoms of element $X$ form $hcp$ lattice and those of element $Y$ occupy $\frac{2}{3}$ of its tetrahedral voids. The percentage of element $X$ in the lattice is ..... . (Nearest integer)

How many tetrahedral voids are occupied in diamond? (in percentage)

$Ga$ (atomic mass $70 \, u$) crystallizes in a hexagonal close packed structure. The total number of voids in $0.581 \, g$ of $Ga$ is $\dots \dots \dots \dots \dots \times 10^{21}$. (Round off to the Nearest Integer).

The number of octahedral and tetrahedral holes respectively present in a hexagonal close packed $(hcp)$ crystal of $X$ atoms are

The packing efficiency in a body centered cubic $(bcc)$ structure is closest to $.... \, \%$

If $z$ represents the number of atoms in a unit cell of a close-packed structure with an $ABCABC$ stacking sequence,then the number of tetrahedral voids in the unit cell is ....