Question

In a compound, atoms of element Y form ccp lattice and those of element X occupy $2/3^{r}d$ of tetrahedral voids. The formula of the compound will be:

• A. $X_4{Y}_3$
• B. $X_2{Y}_3$
• C. $X_{2}Y$
• D. $X_3{Y}_4$

Answer 1

The correct option is A $X_4{Y}_3$

Y occupies CCP lattice hence the effective number of Y = 4 ( effective no of atoms in CCP is 4)

X occupies 2/3 of tetrahedral voids . Number of tetrahedral voids generated in any unit cell is = 2Z ( twice of an effective number of atoms in unit cell )

= 2×4 = 8

Since X occupies 2/3 of tetrahedral voids , so Effective number of X = $\frac{2}{3}\times 8=\frac{16}{3}$

So $X=\frac{16}{3}$ & $Y=4$ ,

Hence simplest formula is $X_4$$Y_3$