The ionic substance strontium oxide, SrO, forms from the reaction of strontium metal with molecular oxygen. The arrangement of the ions in solid SrO is analogous to that in solid NaCl (Figure 2.21):

(a) Write a balanced equation for the formation of SrO(s) from its elements.
(b) Based on the ionic radii in Figure 7.7, predict the length of the side of the cube in the figure (the distance from the center of an atom at one corner to the center of an atom at a neighboring corner).
(c) The density of SrO is 5.10g/cm3. Given your answer to part (b), how many formula units of SrO are contained in the cube shown here?
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Group IA Group 2A Group 3A Group 6A Group 7A Be2+ 0.59 0.90 041 Li 0.90 0.82 0.73 0.71 A13+ 0.68 1.54 Ca2+ 1.14 Ga3+ 1.84 1.82 1.96 1.24 1.16 Rb+ 1.66 0.94 207 2.06 Sr 1.92 In 144 211 -cation anion neutral atom