Predict the shape of CsCl having a radius ratio of 0.93:
Correct answer: C. Body-centered cubic
- A. Tetrahedral
- B. Octahedral
- C. Body-centered cubic
- D. Hexagonal
Explanation
CsCl adopts a body-centered cubic (bcc) arrangement where each Cs⁺ ion is surrounded by 8 Cl⁻ ions and vice versa, giving a coordination number of 8:8.The high radius ratio of 0.93 indicates that the cation is nearly as large as the anion, so the cation can fit comfortably in the cubic void at the body center of the cube formed by Cl⁻ ions.This structure is stable because it minimizes repulsion and maximizes packing efficiency when the cation and anion sizes are comparable.That's why CsCl is a textbook example of an 8-coordination, cubic crystal structure (not simple cubic, but specifically body-centered cubic).
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About Shape of Ionic Crystals
Ionic crystal shape depends on the regular arrangement of oppositely charged ions in a three-dimensional lattice. The topic covers coordination number, radius ratios, lattice geometry and structures such as sodium chloride, caesium chloride and zinc sulfide, which should not be confused with the molecular shapes predicted by VSEPR theory.
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