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

The correct coordination number for the zinc ion in the zinc blende crystal structure is:

What is the coordination number of a particle in $hcp$ structure?

The unit cell of a binary compound of $A$ and $B$ metals has a $ccp$ structure with $A$ atoms occupying the corners and $B$ atoms occupying the centres of each face of the cubic unit cell. If during the crystallisation of this alloy,two $A$ atoms are missing from the unit cell,the overall composition per unit cell is:

The empirical formula for a compound with a cubic close packed arrangement of anions and with cations occupying all the octahedral sites is $A_{x}B$. The value of $x$ is ..... .
(Integer answer)

For an ionic crystal of the type $AB$,the value of the limiting radius ratio is $0.40$. This value suggests that the crystal structure should be: