The superoxide anion,

CHEMISTRY · Multi-part · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties

Problem

The superoxide anion, O2−O_2^{-}, plays a central role in many biological redox processes. Answer the following questions about the electronic structure and properties of O2−O_2^{-}. (a) Calculate the total number of valence electrons in O2−O_2^{-} and show why the species possesses an unpaired electron. (b) Draw every valid Lewis structure for O2−O_2^{-}, including lone pairs, the unpaired electron, and formal charges. (c) Explain how the resonance structures in part (b) account for the overall −1-1 charge of the anion while distributing electron density between the two oxygen atoms. (d) Using your Lewis structures, predict the relative O–O bond order in O2−O_2^{-} compared with that in molecular oxygen (O2O_2) and peroxide (O22−O_2^{2-}). Provide a justification that connects bond order, bond length, and bond strength. (e) Experimental measurements show that the O–O bond length in O2−O_2^{-} is 1.33 A˚1.33\,\text{\AA}. Discuss whether this value is consistent with your prediction in part (d) and explain any discrepancy.

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