Question

A compound alloy of gold and copper crystallizes in a cubic lattice in which gold occupy that lattice point at corners of the cube and copper atom occupy the centres of each of the cube faces. What is the formula of this compound?

• A. $AuC{u}_6$
• B. $AuCu$
• C. $AuC{u}_3$
• D. None of the above

Answer 1

The correct option is C $AuC{u}_3$

Per unit cell, number of atoms of Cu $=\frac{1}{2}\times 6=3$
Number of atoms of Au $=\frac{1}{8}\times 8=1$
Therefore, the compound is ${\text{AuCu}}_3$