The rutile and fluorite structures, shown here (anions are colored green), are two of the most common structure types for ionic compounds where the cation to anion ratio is 1:2.
(a) For CaF2 and ZnF2 use ionic radii, Ca2+, (r=1.14 A°), Zn2+(r=0.88 A°), F- (r=1.19 A°) to predict which compound is more likely to crystallize with the fluorite structure and which with the rutile structure.
(b) What are the coordination numbers of the cations and anions in each of these structures?