Shown below is the cubic unit cell of an ionic compound. Answer the questions by referring to this structure. Be careful to note that some atoms are hidden by those in front.

a. One of the spheres (red or green) represents a monatomic, metallic ion. The other color sphere represents a monatomic, nonmetal ion. Which spheres probably represent the metal ion? Explain.
b. How many red spheres are there in the unit cell? How many green ones?
c. From the information you have, deduce the general formula of the compound, using M for the metallic element and X for the nonmetallic element. What are the formulas of the ions?
d. Give an example of a compound that might have this structure. Explain why you think this compound might have this structure. Which ion of this compound would be represented by the red spheres?