Step 1: Understanding the Topic
This question is about the crystal structures of ionic solids. "Coordination" refers to the arrangement of nearest-neighbor ions around a central ion. Tetrahedral coordination means that each ion is surrounded by four other ions located at the vertices of a tetrahedron. This corresponds to a coordination number (CN) of 4.
Step 2: Key Approach - Identifying Crystal Structures
We need to know the common crystal lattice structures associated with each compound and their corresponding coordination numbers.
Step 3: Detailed Analysis of Each Option
(A) CdI$_2$ (Cadmium Iodide): This compound forms a characteristic layered lattice structure. Each Cadmium ($Cd^{2+}$) ion is surrounded by six Iodide ($I^-$) ions in an octahedral arrangement. Therefore, its coordination is octahedral (CN=6), not tetrahedral.
(B) CsCl (Cesium Chloride): This adopts a structure where each Cesium ($Cs^+$) ion is at the center of a cube with eight Chloride ($Cl^-$) ions at the corners, and vice-versa. This is known as the CsCl structure type. The coordination is cubic (CN=8), not tetrahedral.
(C) ZnS (sphalerite): This is one of the two main polymorphs of Zinc Sulfide. The sphalerite (or zinc blende) structure is based on a face-centered cubic lattice. In this arrangement, each Zinc ($Zn^{2+}$) ion is surrounded by four Sulfide ($S^{2-}$) ions, and each Sulfide ion is surrounded by four Zinc ions. The arrangement is tetrahedral (CN=4).
(D) ZnS (wurtzite): This is the other main polymorph of Zinc Sulfide. The wurtzite structure is based on a hexagonal close-packed lattice. Despite the different overall lattice symmetry, the local coordination environment is the same as in sphalerite. Each ion is surrounded by four ions of the opposite charge in a tetrahedral (CN=4) arrangement.
Step 4: Final Answer
Both the sphalerite and wurtzite forms of ZnS exhibit tetrahedral coordination for their ions.