$$ 2 \mathrm{AgNO}_3(\mathrm{~s}) \stackrel{\Delta}{\longrightarrow} 2 \mathrm{Ag}(\mathrm{s})+2 \mathrm{NO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) $$

Both the $\mathrm{NO}_2$ and $\mathrm{O}_2$ gases are paramagnetic. $\mathrm{NO}_2(\mathrm{~g})$ has 1 unpaired electron and $\mathrm{O}_2(\mathrm{~g})$ has 2 unpaired electrons.

According to MOT,

$$\therefore\,\,\,\,$$ Molecular orbital configuration of O₂ (16 electrons) is

$${\sigma _{1{s^2}}}\,\,\sigma _{1{s^2}}^ * \,$$ $${\sigma _{2{s^2}}}\,\,\sigma _{2{s^2}}^ * \,$$ $${\sigma _{2p_z^2}}\,\,{\pi _{2p_x^2}} = {\pi _{2p_y^2}}\,\,\pi _{2p_x^1}^ * \,\, = \pi _{2p_y^1}^ * $$

$$\therefore\,\,\,\,$$N_a = Anti bonding electrons = 6

N_b = 10

Note :

N_b = Number of electrons in bonding molecular orbital

N_a $$=$$ Number of electrons in anti bonding molecular orbital

(1) $$\,\,\,\,$$ upto 14 electrons, molecular orbital configuration is



Here N_a = Anti bonding electrons $$=$$ 4 and N_b = 10

(2) $$\,\,\,\,$$ After 14 electrons to 20 electrons molecular orbital configuration is - - -



Here N_a = 10

and N_b = 10