Concept:A superoxide is characterized by the presence of the superoxide anion, \( \text{O}_2^- \), where the oxygen has a fractional oxidation state of -1/2.
Solution:- Let's analyze the oxidation state of Oxygen in each option to classify the oxide:
- CaO: Ca is +2. So O is -2. (Normal Oxide).
- \( \text{BaO}_2 \): Ba is +2. The two oxygens must sum to -2. Each O is -1. (Peroxide).
- \( \text{Na}_2\text{O}_2 \): Na is +1. Two Na give +2. The two oxygens sum to -2. Each O is -1. (Peroxide).
- \( \text{RbO}_2 \): Rubidium (Group 1) is +1. Therefore, the \( \text{O}_2 \) unit must have a total charge of -1. Each Oxygen atom has an oxidation state of -1/2. This defines a superoxide.
Why other options are incorrect:- Only heavy alkali metals (like K, Rb, Cs) are large enough to stabilize the superoxide ion. Options A, B, and C are normal oxides or peroxides.
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