Question

Which of the following has tetrahedral coordination?

• A. CdI$_2$
• B. CsCl
• C. ZnS (sphalerite)
• D. ZnS (wurtzite)

Hint:

ZnS exists in two polymorphic forms: zinc blende (cubic) and wurtzite (hexagonal). Both have coordination number 4 (tetrahedral).

Answer 1

The Correct Option is C

Step 1: Understand tetrahedral coordination.
In tetrahedral coordination, each cation is surrounded by 4 anions arranged at the corners of a tetrahedron.
Coordination number = 4.
Step 2: Analyze each compound.
(A) CdI$_2$ → Layered structure → Octahedral coordination (Coordination number = 6).
(B) CsCl → Cubic structure → Coordination number = 8 (body-centered cubic type).
(C) ZnS (sphalerite) → Zinc blende structure → Each Zn$^{2+}$ surrounded by 4 S$^{2-}$ → Tetrahedral coordination.
(D) ZnS (wurtzite) → Hexagonal structure → Also tetrahedral coordination (Coordination number = 4).
Step 3: Conclusion.
Both sphalerite and wurtzite forms of ZnS have tetrahedral coordination.