Both ZnS and CaF 2 have a face-centered cubic unit cell where the S 2- and Ca 2+ ions are closest packed in each structure .Which of the following is true?
A) There are 4 tetrahedral holes empty in each structure.
B) In both compounds, one-half of the tetrhedral holes are filled.
C) In both compounds, all the tetrhedral holes are filled.
D) In ZnS, one-half of the tetrahedral holes are filled by Zn 2+ ions, whereas in CaF 2 all the tetrahedral holes are filled with F - ions.
E) There are 8 Zn 2+ ions and 4 F - ions in the unit cell.

Question

Quizplus · Accepted Answer

In ZnS, the cations (Zn) occupy half of the tetrahedral holes, leaving the other half empty. In CaF₂, the anions (F) occupy all of the tetrahedral holes. Therefore, option D is the correct answer. Option A is incorrect because there are only 4 tetrahedral holes in a face-centered cubic unit cell, and they cannot all be empty in both compounds. Option B is incorrect because only one of the compounds has half of the tetrahedral holes filled. Option C is incorrect because all of the tetrahedral holes are not filled in both compounds. Option E is incorrect because the number of ions in the unit cell for each compound is not provided in the question.

Both ZnS and CaF2 Have a Face-Centered Cubic Unit Cell

Both ZnS and CaF₂ Have a Face-Centered Cubic Unit Cell