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

question 85

Multiple Choice

Both ZnS and CaF₂ have a face-centered cubic unit cell where the S^2- and Ca²⁺ 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.