$\therefore \quad \mathrm{B} . \mathrm{O}.=\frac{10-4}{2}=3$

$\mathrm{N}_{2}^{-}:(\sigma 1 s)^{2}\left(\sigma^{*} 1 s\right)^{2}(\sigma 2 s)^{2}\left(\sigma^{*} 2 s\right)^{2}\left(\pi 2 p_{x}\right)^{2}$

$\left(\pi 2 p_{y}\right)^{2}\left(\sigma 2 p_{z}\right)^{2}\left(\pi^{*} 2 p_{x}\right)^{1}$

$\therefore \quad \mathrm{B}. \mathrm{O}.=\frac{10-5}{2}=2.5$

$\mathrm{N}_{2}^{2-}:(\sigma 1 s)^{2}\left(\sigma^{*} 1 s\right)^{2}(\sigma 2 s)^{2}\left(\sigma^{*} 2 s\right)^{2}\left(\pi 2 p_{x}\right)^{2}$

$\left(\pi 2 p_{y}\right)^{2}\left(\sigma 2 p_{z}\right)^{2}\left(\pi^{*} 2 p_{x}\right)^{1}\left(\pi^{*} 2 p_{y}\right)^{1}$

$\therefore \quad \mathrm{B} . \mathrm{O} .=\frac{10-6}{2}=2$

Hence the order: $\mathrm{N}_{2}^{2-}<\mathrm{N}_{2}^{-}<\mathrm{N}_{2}$