Ionic Radii
     Zn²⁺, 74 pm
     S^2-, 184 pm
Radius Ratio = 74/184 = 0.40

Zinc blende is the cubic form of ZnS. There is also a hexaginal form that we will not discuss. The radius ratio is such that we expect the zinc ions to occupy tetrahedral holes in a close packed array of sulfide ions.

The stoichiometry (one Zn²⁺ ion per
S^2- ion) requires that only one-half of the tetrahedral holes be occupied.

Click on the layer of sulfide ions to the right to see the ZnS structure. The links above go to definitions.