In Chapter 7 we saw that Li reacts with oxygen to form lithium oxide, Li2O, while the la...

In Chapter 7 we saw that Li reacts with oxygen to form lithium oxide, Li₂O, while the larger alkali metals react with oxygen to form peroxides (such as etc.). The origin of this curious pattern of reactivity is related to the relative sizes of the cation and anion and the overall stoichiometry. Li2O crystallizes with a structure called the antifluorite structure. This structure is identical to the fluorite structure shown' in Figure 11.42(c) but the cations and anions have been switched. (a) In Li₂O, what are the coordination numbers for each ion) (b) As the cation radius increases, would you expect the coordination number to increase or decrease (assuming the anion size does not change)? (c) Why do you think the antifluorite structure becomes unstable for A₂O (A = Li, Na, K, Rb, Cs) compounds of the heavier alkali metal ions? :