Assertion : The oxygen-oxygen bond length in peroxide ion ( O_2^ 2-...

The number of electrons in superoxide ion $O_2^-$ is $17$.

The molecular orbital electronic configuration of $O_2^-$ is \sigma_{1s}^2 \sigma^{*}_{1s}^2 \sigma_{2s}^2 \sigma^{*}_{2s}^2 \sigma_{2p_z}^2 \pi_{2p_x}^2 \pi_{2p_y}^2 \pi^{*}_{2p_x}^2 \pi^{*}_{2p_y}^1.

Bond order of $O_2^- = \dfrac{10 - 7}{2} = 1.5$.

The number of electrons in peroxide ion $O_2^{2-}$ is $18$.

The molecular orbital electronic configuration of $O_2^{2-}$ is \sigma_{1s}^2 \sigma^{*}_{1s}^2 \sigma_{2s}^2 \sigma^{*}_{2s}^2 \sigma_{2p_z}^2 \pi_{2p_x}^2 \pi_{2p_y}^2 \pi^{*}_{2p_x}^2 \pi^{*}_{2p_y}^2.

Bond order of $O_2^{2-} = \dfrac{10 - 8}{2} = 1$.

Since bond length is inversely proportional to bond order, the oxygen-oxygen bond length in peroxide ion is greater than that in superoxide ion.

Both assertion and reason are true and reason is the correct explanation of assertion.

Answer: If both assertion and reason are true and reason is the correct explanation of assertion.