Question

In an ionic crystalline solid atoms of element Y form hcp lattice. The atoms of element X occupy one third of tetrahedral voids. What is the formula of the compound ?

Answer 1

In the given hcp lattice, Y atoms are present at 12 corners and 2 face centres.

∴ Number of Y atoms = \(\frac{1}{6}×12 +\frac{1}{2}×2 \) = 2+1= 3

There are 6 tetrahedral voids, the number of X atoms = \(\frac{1}{3}×6\) = 2

∴ Formula of the compound is X₂Y₃.