Atoms $A$ are arranged in an $FCC$ system,and atoms $B$ occupy all the octahedral voids and half of the tetrahedral voids. The formula of the compound is:

Packing fraction of a layer in $2D$ hexagonal close packing arrangement is:

$A$ compound is formed by cation $C$ and anion $A$. The anions form hexagonal close packed $(hcp)$ lattice and the cations occupy $75 \%$ of octahedral voids. The formula of the compound is

$A$ compound is formed by elements $A$ and $B$. Element $B$ forms an $HCP$ lattice,and element $A$ occupies $2/3$ of the tetrahedral voids. What is the formula of the compound formed by $A$ and $B$?

$A$ compound is formed by two elements $A$ and $B$. The element $B$ forms a cubic close-packed $(CCP)$ structure and atoms of $A$ occupy $\frac{1}{3}$ of the tetrahedral voids. If the formula of the compound is $A_x B_y$,then the value of $x+y$ is:

In a compound,atoms of element $Y$ form $ccp$ lattice and those of element $X$ occupy $2/3$ of tetrahedral voids. The formula of the compound will be