( i )
Structure in which P cations are located at the corners of the unit cell and six Q anions on the center of all the cubic faces.
( ii )
coordination number of Q is " 12 " due to fcc arrangement .
( iii )
formula of the compound is PQ3 .
effective number of atoms of p = 1/8 * 8 = 1 ( due to all corners )
effective number of atoms of q = 1/2 * 6 = 3 ( due to all face center )