Question:

In ionic solid, anions are arranged in ccp array and cations occupy $1/3$ tetrahedral voids. What is the formula of ionic compound?
[Consider $\text{A} = \text{cation}; \text{B} = \text{anion}$]

Show Hint

Tet voids = $2 \times$ Atoms; Oct voids = Atoms.
Updated On: May 14, 2026
  • $\text{AB}_3$
  • $\text{A}_2\text{B}_3$
  • $\text{A}_3\text{B}_2$
  • $\text{AB}_4$
Show Solution
collegedunia
Verified By Collegedunia

The Correct Option is B

Solution and Explanation


Step 1: Concept
In a ccp (or fcc) lattice, if the number of atoms is $N$, the number of tetrahedral voids is $2N$.

Step 2: Meaning
Let the number of anions (B) be $N$. Then number of tetrahedral voids is $2N$.

Step 3: Analysis
Cations (A) occupy $1/3$ of tetrahedral voids.
Number of A = $\frac{1}{3} \times 2N = \frac{2N}{3}$.
Ratio A : B = $\frac{2N}{3} : N = 2 : 3$.

Step 4: Conclusion
The chemical formula is $\text{A}_2\text{B}_3$. Final Answer: (B)
Was this answer helpful?
0
0