JEE Advanced 2022 · Paper 2, Chemistry question 5

Decomposition.
$$\ce{2AgNO3 -> 2Ag + 2NO2 + O2}.$$
Both gases are paramagnetic: $\ce{NO2}$ has 1 unpaired electron and $\ce{O2}$ has 2. So the gas meant is $\ce{O2}$.

MO configuration of $\ce{O2}$ (16 electrons):
$$\sigma_{1s}^2\,\sigma_{1s}^{*2}\,\sigma_{2s}^2\,\sigma_{2s}^{*2}\,\sigma_{2p_z}^2\,\pi_{2p}^4\,\pi_{2p}^{*2}.$$

Antibonding electrons. $2+2+2=6$.