How many particles per unit cell are present in $BCC$ structure?

The coordination number of $Na^{+}$ in $NaCl$ is

$A$ compound having elements $X$ and $Y$ crystallises in a cubic structure, where $X$ is at the corner position and $Y$ is at the center of the cube. The correct formula of the compound is

For some crystals,the radius ratio for cation and anion is $0.525$,its coordination number will be

In the $NaCl$ structure,what is the position of $Cl^-$ ions?

$A$ solid $AB$ has a $ZnS$ type structure. If the radius of the $B^-$ ion is $100 \, pm$, what is the minimum radius of the $A^+$ cation in $pm$?