An ionic compound is formed by elements X and Y. Element Y forms a face-centered cubic (FCC) lattice, and element X occupies one-third of the tetrahedral voids. What is the formula of the compound?

Step-by-step solution

Element Y forms a face-centered cubic (FCC) lattice. Number of Y atoms per unit cell = 4 Number of tetrahedral voids in an FCC unit cell = 2 4 = 8 Element X occupies one-third of the tetrahedral voids. Number of X atoms per unit cell = 1 3 8 = 8 3 Ratio of X to Y = 8 3 : 4 = 8 : 12 = 2 : 3 The formula of the compound is X₂Y₃ .