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?

$A$ solid has $CCP$ arrangement having atoms $A, B, C$. If $A$ atoms are present at face centres,$B$ at corners and $C$ atoms occupy $50\%$ tetrahedral voids,then the molecular formula of the solid will be:

Calculate the number and position of tetrahedral and octahedral voids in a $ccp$ or $fcc$ structure.

$Ag$ crystallises in $fcc$ lattice. What is the total number of tetrahedral voids present in $540 \ g$ of $Ag$ metal (in $N_A$)? $(N_A = \text{Avogadro number}; Ag \text{ atomic weight} = 108 \ g \ mol^{-1})$

If the radius of the octahedral void is $r$ and the radius of the atoms in close packing is $R$,derive the relation between $r$ and $R$.

What is the packing efficiency of $fcc$ crystal structure (in $\%$)?