Atoms of element $B$ form $hcp$ lattice and those of the element $A$ occupy $2/3$ of tetrahedral voids. What is the formula of the compound formed by the elements $A$ and $B$?

In a cubic close packing,the unit cell has...

In a face-centered cubic $(FCC)$ close-packed structure,the third layer covers the ..... voids created between the first and second layers.

What is the number of octahedral and tetrahedral voids present respectively in $0.25 \ mol$ of a substance having $hcp$ structure?

Consider the $bcc$ unit cells of the solid $1$ and $2$ with the position of atoms as shown below. The radius of atom $B$ is twice that of atom $A$. The unit cell edge length is $50\%$ more in solid $2$ than in $1$. What is the approximate packing efficiency in solid $2$? $........... \%$

$A$ 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: