Question

Atoms of element B form hcp lattice and those of the element A occupy $\frac{2}{3}$rd of tetrahedral voids. What is the formula of the compound formed by the elements A and B?

• A. $A_4{B}_3$
• B. $A_2{B}_3$
• C. $A_3{B}_4$
• D. $A_3{B}_2$

Answer 1

The correct option is A $A_4{B}_3$

The number of tetrahedral voids formed is equal to twice the number of atoms of element B and only 2/3rd of these are occupied by the atoms of element A. Hence the ratio of the number of atoms of A and B is $2\times \frac{2}{3}:1or4:3$ and the forrnula of the compound is $A_4{B}_3$ .