QuestionSolid state / radius ratio, covalency
For ZnS, a radius ratio (r_{Zn²⁺}/r_{S²⁻}) of 0·52 suggests a coordination number, of 6 for both cation and anion. However, in reality, ZnS adopts a coordination number of 4 : 4. This is because
- (a) ZnS is a true covalent compound
- (b) ZnS is an ionic compound with considerable covalency
- (c) Zn²⁺ is too small to occupy octahedral holes
- (d) S²⁻ ions are too large to provide higher coordination number to Zn²⁺
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