[" 83.Edge length of "M^(+)X^(-)" (fcc structure) is "7.2@A" ."],[" Assuming "M^(+)-X^(-)" contact along the cell "],[" edge,radius of "X^(-)" ion is "(r_(M+)=1.6A):L3],[" 1) "2.0A" 2) "5.6A" ?) "2.8A^(@)" ."]