Question

Peroxide and superoxide ions are, respectively:
A. diamagnetic and diamagnetic
B. paramagnetic and paramagnetic
C. paramagnetic and diamagnetic
D. diamagnetic and paramagnetic

Answer 1

Magnetic character of molecules most commonly determined by the number of unpaired electrons present in the molecule. Paramagnetic substances are weakly magnetized in the presence of an external magnetic field. Diamagnetic substances have a tendency to move from the stronger part to the weaker part of the external magnetic field.

Complete step by step solution:
Paramagnetic materials are attracted by external magnetic fields and at least one unpaired electron in the system. The magnetic field created by paramagnetic materials is in the direction of the external magnetic field. Paramagnetic is a stronger magnetic behavior exhibited only by selective materials.
Diamagnetic materials are repelled by external magnetic fields, but they have all their electrons paired. Magnetic fields created by diamagnetic materials are opposing in direction to the external magnetic field. Diamagnetism is a weak magnetic behavior generally shown by all materials.
Superoxide ion $({O_2}^-)$ Molecular Orbital configuration of $({O_2}^-)$ ion is
Superoxide ions has $8 + 8 + 1 = 17$ electrons.
The M.O configuration is$({O_2}^-)$ is
$\sigma 1{s^2},\sigma ^*1{s^2},\sigma 2{s^2},\sigma ^*2{s^2},\sigma 2p{x^2},\pi ^*2p{y^2} = {\text{ }}\pi 2p{z^2},\pi ^*2p{y^2} = \pi ^*2p{z^1},\sigma ^*2p{x^0}.$
The superoxide ion $({O_2}^-)$ will have one unpaired electron and therefore will be paramagnetic.
Peroxide ion $({O_2}^{2-})$ Molecular Orbital configuration of $({O_2}^{2-})$ ion:
Peroxide ion has $8 + 8 + 2 = 18$ electrons.
The M.O configuration is:
$({O_2}^-) = \;\sigma 1{s^2},\sigma ^*1{s^2},\sigma 2{s^2},\sigma ^*2{s^2},\sigma 2p{x^2},{\text{ }}\pi 2p{y^2} = {\text{ }}\pi 2p{z^2},\pi ^*2p{y^2} = \pi ^*2p{z^2},\sigma ^*2p{x^0}.$
Peroxide ion $({O_2}^{2-})$ doesn't have any unpaired electrons and is diamagnetic.
Therefore peroxide and superoxide ions are diamagnetic and paramagnetic respectively.

**So, option (D) is Correct

Note:**
Peroxide is more stable than superoxide Peroxide ${O_2}\left( {^{2 - }} \right)$ ion has all its valence electrons spin-paired.
Superoxide ${O_2}\left( {^{1 - }} \right)$ ion has one of its electrons unpaired. It is a radical, and radicals generally more reactive than spin-paired compounds or ions.