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Question: Answered & Verified by Expert
The pairs of species of oxygen and their magnetic behaviours are noted below. Which of the following presents the correct description?
ChemistryChemical Bonding and Molecular StructureNEETNEET 2011 (Mains)
Options:
  • A $\mathrm{O}_2^{-}, \mathrm{O}_2^{2-}$ - Both diamagnetic
  • B $\mathrm{O}^{+}, \mathrm{O}_2^{2-}$ - Both paramagnetic
  • C $\mathrm{O}_2^{+}, \mathrm{O}_2$ - Both paramagnetic
  • D $\mathrm{O}, \mathrm{O}_2^{2-}$ - Both paramagnetic
Solution:
1902 Upvotes Verified Answer
The correct answer is: $\mathrm{O}_2^{+}, \mathrm{O}_2$ - Both paramagnetic
The molecular orbital configurations of $\mathrm{O}_2^{+}, \mathrm{O}_2^{-}, \mathrm{O}_2^{2-}$ and $\mathrm{O}_2$ are
$$
\begin{aligned}
& \mathrm{O}_2^{+}=\sigma 1 s^2, \sigma 1 s^2, \sigma 2 s^2, \sigma 2 s^2, \sigma 2 p_z^2, \pi 2 p_x^2 \approx \pi 2 p_y^2, \\
& \pi 2 p_x^1 \approx \pi 2 p_y^0 \\
& \mathrm{O}_2^{-}=\sigma 1 s^2, \sigma \cdot \% 1 s^2, \sigma 2 s^2, \sigma 2 s^2, \sigma 2 p_z^2, \pi 2 p_x^2 \\
& \approx \pi 2 p_y^2, \pi 2 p_x^2 \approx \pi 2 p_y^1 \\
& \mathrm{O}_2^{2-}=\sigma 1 s^2, \sigma \cdot s^2, \sigma 2 s^2, \sigma 2 s^2, \sigma 2 p_z^2, \pi 2 p_x^2 \\
& \approx \pi 2 p_y^2, \pi 2 p_x^2 \approx \pi 2 p_y^2 . \\
& \mathrm{O}_2=\sigma 1 s^2, \sigma 1 s^2, \sigma 2 s^2, \sigma^* 2 s^2, \sigma 2 p_z^2, \pi 2 p_x^2 \\
& \approx \pi 2 p_y^2, \pi 2 p_x^1 \approx \pi 2 p_y^1
\end{aligned}
$$
And the electronic configuration of $\mathrm{O}$ and $\mathrm{O}^{+}$ are
$$
\begin{array}{r}
\mathrm{O}=1 s^2, 2 s^2, 2 p_x^2, 2 p_y^1, 2 p_z^1 \\
\mathrm{O}^{+}=1 s^2, 2 s^2, 2 p_x^1, 2 p_y^1, 2 p_z^1
\end{array}
$$
As $\mathrm{O}_2^{+}, \mathrm{O}_2, \mathrm{O}_2^{-}, \mathrm{O}$ and $\mathrm{O}^{+}$have unpaired electrons, hence are paramagnetic.

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