MgO and CaS both adopt a similar crystal structure. The distance between cations and anions is the only distinction between the two. Estimate the Mg–O and the Ca–S distances. Use the following information:

• A. Mg–O: 2.12 Å; CaS: 2.84 Å
• B. Mg–O: 2.40 Å; CaS: 2.56 Å
• C. Mg–O: 2.07 Å; CaS: 2.81 Å
• D. Mg–O: 2.46 Å; CaS: 2.42 Å

Answer: (A)