The so-called pyroanions, X₂O₇^n-, form a series of structurally similar polyatomic anions for the elements Si, P, and S.

(a) Draw the Lewis structures of these anions, and predict the geometry of the anions. What is the maximum number of atoms that can lie in a plane?

(b) Each pyroanion in part (a) corresponds to a pyroacid, X₂O₇Hn. Compare each pyroacid to the acid containing only one atom of the element in its maximum oxidation state. From this comparison, suggest a strategy for the preparation of these pyroacids.

(c) What is the chlorine analogue of the pyroanions? For which acid is this species the anhydride?