Question

Which one of the following is paramagnetic?

• A. ${\mathrm{O}}_3$
• B. ${\mathrm{N}}_2$
• C. $\mathrm{CO}$
• D. ${\mathrm{O}}_2$

Answer 1

The correct option is D

${\mathrm{O}}_2$

Explanation for correct option:

D. ${\mathrm{O}}_2$

Paramagnetic material:

• The material that is weakly attracted by a magnetic field is known as Paramagnetic material
• Paramagnetic substances have unpaired electrons.

Oxygen:

• ${\mathrm{O}}_2$ has 16 valence electrons.
• The electronic configuration of ${\mathrm{O}}_2$: ${\left(\mathrm{\sigma }1\mathrm{s}\right)}^2{(\mathrm{\sigma }*1\mathrm{s})}^2{\left(\mathrm{\sigma }2\mathrm{s}\right)}^2{(\mathrm{\sigma }*2\mathrm{s})}^2{\left(\mathrm{\sigma }2\mathrm{pz}\right)}^2(\mathrm{\pi }2{\mathrm{px}}^2=\mathrm{\pi }2{\mathrm{py}}^2)(\mathrm{\pi }*2{\mathrm{px}}^1=\mathrm{\pi }*2{\mathrm{py}}^1)$.
• It is paramagnetic in nature as it has two unpaired electrons.

Explanation for incorrect options:

A. ${\mathrm{O}}_3$

• ${\mathrm{O}}_3$ has 24 valence electrons.
• It has no unpaired electrons. Thus, it is diamagnetic.

B. ${\mathrm{N}}_2$

• ${\mathrm{N}}_2$ has 14 valence electrons.
• The electronic configuration of ${\mathrm{N}}_2$: ${\left(\mathrm{\sigma }1\mathrm{s}\right)}^2{(\mathrm{\sigma }*1\mathrm{s})}^2{\left(\mathrm{\sigma }2\mathrm{s}\right)}^2{(\mathrm{\sigma }*2\mathrm{s})}^2{\left(\mathrm{\sigma }2\mathrm{pz}\right)}^2(\mathrm{\pi }2{\mathrm{px}}^2=\mathrm{\pi }2{\mathrm{py}}^2)(\mathrm{\pi }*2{\mathrm{px}}^2=\mathrm{\pi }*2{\mathrm{py}}^2)$
• It has no unpaired electrons. Thus, it is diamagnetic.

C. $\mathrm{CO}$

• $\mathrm{CO}$ has 14 valence electrons.
• The electronic configuration of $\mathrm{CO}$: ${\left(\mathrm{\sigma }1\mathrm{s}\right)}^2{(\mathrm{\sigma }*1\mathrm{s})}^2{\left(\mathrm{\sigma }2\mathrm{s}\right)}^2{(\mathrm{\sigma }*2\mathrm{s})}^2{\left(\mathrm{\sigma }2\mathrm{pz}\right)}^2(\mathrm{\pi }2{\mathrm{px}}^2=\mathrm{\pi }2{\mathrm{py}}^2)(\mathrm{\pi }*2{\mathrm{px}}^2=\mathrm{\pi }*2{\mathrm{py}}^2)$
• It has no unpaired electrons. Thus, it is diamagnetic.

Hence, the correct option is D i.e. ${\mathrm{O}}_2$.