Question

Classify each of the species given below as para-magnetic or diamagnetic

Classify each of the species given below as paramagnetic or diamagnetic.

Answer 1

Concepts and reason

The given problem is based on the concept of Molecular Orbital Theory (MOT). The MOT can be used to predict whether the molecule is paramagnetic or diamagnetic.

If all the electrons are paired, the molecule is diamagnetic and if the molecule has one or more unpaired electrons, it is paramagnetic.

Fundamentals

To classify the molecules as paramagnetic or diamagnetic, write the molecular orbital configurations of the molecules based on MOT. Then classify on the basis of paired and unpaired electrons.

The molecular orbital configuration of ${{\rm{O}}_{\rm{2}}}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\sigma 2p_x^2\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\left\{ {{\pi ^*}2p_y^1,{\pi ^*}2p_z^1} \right\}$

The molecular orbital configuration of ${\rm{O}}_2^{2 - }$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\sigma 2p_x^2\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\left\{ {{\pi ^*}2p_y^2,{\pi ^*}2p_z^2} \right\}$

The molecular orbital configuration of ${\rm{O}}_2^{2 + }$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\sigma 2p_x^2\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}$

Hence, ${{\rm{O}}_{\rm{2}}}$ is paramagnetic as it has two unpaired electrons. ${\rm{O}}_2^{2 - }$ and ${\rm{O}}_2^{2 + }$ are diamagnetic as all the electrons are paired.

The molecular orbital configuration of F₂ is:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\sigma 2p_x^2\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\left\{ {{\pi ^*}2p_y^2,{\pi ^*}2p_z^2} \right\}$

The molecular orbital configuration of ${\rm{F}}_2^{2 + }$ is:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\sigma 2p_x^2\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\left\{ {{\pi ^*}2p_y^1,{\pi ^*}2p_z^1} \right\}$

The molecular orbital configuration of ${\rm{F}}_2^{2 - }$ is:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\sigma 2p_x^2\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\left\{ {{\pi ^*}2p_y^2,{\pi ^*}2p_z^2} \right\}{\sigma ^*}2p_x^2$

Hence, F₂ and ${\rm{F}}_2^{2 - }$ are diamagnetic and ${\rm{F}}_2^{2 + }$ is paramagnetic.

The molecular orbital configuration of ${{\rm{N}}_2}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\sigma 2p_x^2$

The molecular orbital configuration of ${\rm{N}}_{\rm{2}}^{\rm{ + }}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\sigma 2p_x^1$

The molecular orbital configuration of ${\rm{N}}_{\rm{2}}^ -$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\sigma 2p_x^2\left\{ {{\pi ^*}2p_y^1,{\pi ^*}2p_z^0} \right\}$

The molecular orbital configuration of ${\rm{N}}_{\rm{2}}^{{\rm{2 + }}}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}$

Hence, ${{\rm{N}}_2}$ and ${\rm{N}}_2^{2 + }$ are diamagnetic while ${\rm{N}}_{\rm{2}}^{\rm{ + }}$ and ${\rm{N}}_{\rm{2}}^ -$ are paramagnetic.

The molecular orbital configuration of ${{\rm{C}}_2}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}$

The molecular orbital configuration of ${\rm{C}}_{\rm{2}}^{{\rm{2 + }}}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^1,\pi 2p_z^1} \right\}$

The molecular orbital configuration of ${\rm{C}}_{\rm{2}}^{2 - }$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}\sigma 2p_x^2$

Hence, ${{\rm{C}}_2}$ and ${\rm{C}}_{\rm{2}}^{{\rm{2 - }}}$ are diamagnetic while ${\rm{C}}_{\rm{2}}^{{\rm{2 + }}}$ is paramagnetic.

The molecular orbital configuration of ${{\rm{B}}_2}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^1,\pi 2p_z^1} \right\}$

The molecular orbital configuration of ${\rm{B}}_{\rm{2}}^{{\rm{2 + }}}$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}$

The molecular orbital configuration of ${\rm{B}}_{\rm{2}}^{2 - }$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}\sigma {}^*2{s^2}\left\{ {\pi 2p_y^2,\pi 2p_z^2} \right\}$

Hence, ${{\rm{B}}_2}$ is paramagnetic while ${\rm{B}}_{\rm{2}}^{{\rm{2 + }}}$ and ${\rm{B}}_{\rm{2}}^{2 - }$ are diamagnetic.

The molecular orbital configuration of ${{\rm{H}}_2}$ is as follows:

$\sigma 1{s^2}$

The molecular orbital configuration of ${\rm{H}}_{\rm{2}}^ -$ is as follows:

$\sigma 1{s^2}{\sigma ^*}1{s^1}$

Hence, ${{\rm{H}}_2}$ is diamagnetic and ${\rm{H}}_{\rm{2}}^ -$ is paramagnetic.

Ans:

O₂ is paramagnetic, while ${\rm{O}}_2^{2 - }$ and ${\rm{O}}_2^{2 + }$ are diamagnetic.

F₂ and ${\rm{F}}_2^{2 - }$ are diamagnetic and ${\rm{F}}_2^{2 + }$ is paramagnetic.

${{\rm{N}}_2}$ and ${\rm{N}}_2^{2 + }$ are diamagnetic while ${\rm{N}}_{\rm{2}}^{\rm{ + }}$ and ${\rm{N}}_{\rm{2}}^ -$ are paramagnetic.

${{\rm{C}}_2}$ and ${\rm{C}}_{\rm{2}}^{2 - }$ are diamagnetic while ${\rm{C}}_{\rm{2}}^{{\rm{2 + }}}$ is paramagnetic.

${{\rm{B}}_2}$ is paramagnetic while ${\rm{B}}_{\rm{2}}^{{\rm{2 + }}}$ and ${\rm{B}}_{\rm{2}}^{2 - }$ are diamagnetic.

${{\rm{H}}_2}$ is diamagnetic and ${\rm{H}}_{\rm{2}}^ -$ is paramagnetic.