In a compound,atoms of element $Y$ form a $ccp$ lattice and atoms of element $X$ occupy $2/3$ of the tetrahedral voids. What is the formula of the compound?

In an ionic solid,anions $(B)$ are arranged in a $ccp$ array and cations $(A)$ occupy $1/3$ of the tetrahedral voids. What is the formula of the ionic compound?

$A$ 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:

$A$ body-centred cubic $(BCC)$ lattice is made up of two different types of atoms $X$ and $Y$. Atom $X$ occupies the body centre and atoms $Y$ occupy the corner positions. One of the corners is left unoccupied per unit cell. The empirical formula of it is

With the help of a labelled diagram,show that there are $4$ octahedral voids per unit cell in a cubic close-packed $(CCP)$ structure.

In an ionic oxide,the oxide anions form an $hcp$ arrangement,while the metal cations occupy $\frac{2}{3}$ of the octahedral voids. Determine the formula of this oxide.