Calcium sulfide has a face-centered cubic unit cell with calcium ions in octahedral holes.How many ions of each element are contained in each unit cell?
A) 1 calcium ion; 1 sulfide ion
B) 2 calcium ions; 2 sulfide ions
C) 2 calcium ions; 4 sulfide ions
D) 4 calcium ions; 2 sulfide ions
E) 4 calcium ions; 4 sulfide ions

Question

Quizplus · Accepted Answer

In a face-centered cubic unit cell, there are 4 sulfide ions (one from each corner contributing 1/8 and one from each face contributing 1/2). Calcium ions occupy all octahedral holes, which are also 4 per unit cell. Thus, there are 4 calcium ions and 4 sulfide ions per unit cell.

Calcium Sulfide Has a Face-Centered Cubic Unit Cell with Calcium