Question

An ionic compound has a unit cell consisting of $A$ ions at the corners of a cube and $B$ ions on the centres of the faces of the cube. The empirical formula for this compound would be:

• A. $A_{3}B$
• B. $A{B}_3$
• C. $A_{2}B$
• D. $AB$

Answer 1

The correct option is B $A{B}_3$

Number of $A$ ions in the unit cell
$=\frac{1}{8}=1$
Number of $B$ ions in the unit cell
$=\frac{1}{2}\times 6=3$
Hence, empirical formula of the compound $=A{B}_3$