Question

The transport of ${\mathit{O}}_{\mathbf{2}}$in the blood is carried out by haemoglobin. Carbon monoxide can interfere with oxygen transport because haemoglobin has a stronger affinity for CO than for ${\mathit{O}}_{\mathbf{2}}$. If is present, normal uptake of ${\mathit{O}}_{\mathbf{2}}$ is prevented, depriving the body of needed oxygen. Using the molecular orbital model write the electronic configuration, give two property differences between CO and${\mathit{O}}_{\mathbf{2}}$

Short answer

The MO filling order for O is as follows:${\sigma }_{1s}{{\sigma }^{*}}_{1s}{\sigma }_{2s}{{\sigma }^{*}}_{2s}{\pi }_{2px}{\pi }_{2py}{\sigma }_{2pz}{{\pi }^{*}}_{2px}{{\pi }^{*}}_{2px}{{\sigma }_{2pz}}^{*}$

Step-by-step solution

Step 1 

The MO filling is as follows for $O_2$:

${{\sigma }^2}_{1s}({{\sigma }^{*}}_{1s}{)}^2{{\sigma }^2}_{2s}({{\sigma }^{*}}_{2s}{)}^2{\sigma }_{2pz}^2{{\pi }^2}_{2px}{\pi }_{2py}^2{\pi }_{2px}^{*}{\pi }_{2py}^{*}$

The MO filling is as follows for CO :

${{\sigma }^2}_{1s}({{\sigma }^{*}}_{1s}{)}^2{{\sigma }^2}_{2s}({{\sigma }^{*}}_{2s}{)}^2{\sigma }_{2pz}^2{{\pi }^2}_{2px}{\pi }_{2py}^2$

Step 2:

From this, it is clear that the oxygen molecule has electrons in the antibonding orbital so it is more unstable and less reactive.

And carbon monoxide has valence electrons in bonding molecular orbital hence its is more reactive than an oxygen molecule.

Also, oxygen is paramagnetic in nature and carbon monoxide is diamagnetic.