An ionic compound of iron and sulfur has a crystal structure in which sulfide ions create an fcc lattice and iron ions occupy half of the available tetrahedral holes.What is the empirical formula of the compound?

Question

Quizplus · Accepted Answer

In a face-centered cubic (fcc) lattice of sulfide ions, there are 4 sulfide ions per unit cell. If iron ions occupy half of the tetrahedral holes, since there are 8 tetrahedral holes in an fcc unit cell, half of these would be 4. Thus, for every 4 sulfide ions, there are 4 iron ions, giving an empirical formula of FeS.

An Ionic Compound of Iron and Sulfur Has a Crystal