The energy of `sigma2p_(z)`, molecular orbital is greater than `pi2p_(x)` and `pi2p_(y)` molecular orbitals in nitrogen molecule. Write the complete sequence of energy levels in the increasing order of energy in the molecule. Compare the relative stability and the magnetic behaviour of the following species.
`N_(2), N_(2)^(+), N_(2)^(-), N_(2)^(2+)`

Explanation

Electronic configuration of N-atom (Z=7) is `1s^(2)2s^(2)2p_(x)^(1)2p_(y)^(1)2p_(z)^(1)`. Total number of electrons present in `N_(2)` molecule is 14,7 from each N-atom. From the views of various rules for filling of molecular orbitals, the electronic configuration of `N_(2)` molecule will be
`sigma1s^(2), sigma^(star)1s^(2), sigma2s^(2), sigma^(star)2s^(2), pi2p_(x)^(2)=pi2p_(y)^(2), sigma2p_(z)^(2)`
Comparative study of hte relative stability and the magnetic behaviour of the following species
i) `N_(2)` molecule `sigma1s^(2), sigma^(star)1s^(2), sigma2s^(2), sigma^(star)2s^(2), pi2p_(x)^(2)=pi2p_(y)^(2), sigma2p_(z)^(2)`
Here, `N_(b)=10`, `N_(a)=4`
Hence, Bond order =`1/2(N_(b)-N_(a))=1/2(10-4)=`
Hence, presence of no unpaired electron indicates it to be diamagnetic.
ii) `N_(2)^(+)` ion `sigma1s^(2), sigma^(star)1s^(2), sigma2s^(2), sigma^(star)2s^(2), pi2p_(x)^(2)~~pi2p_(y)^(2), sigma2p_(z)^(1)`
Here, `N_(b)=9, N_(a)=4` so that BO=`1/2(9-4)=5/2=2.5`
Further, as `N_(2)^(+)` ion has one unpaired electron in the `sigma(2p_(z))` orbital, it is paramagnetic in nature.
iii) `N_(2)^(-)` ions `sigma1s^(2), sigma^(star)s^(2), sigma2s^(2), sigma^(star)2s^(2), pi2p_(x)^(2)=pi2p_(y)^(2), sigma2p_(z)^(2),pi^(star)p_(z)^(1)`
Here, `N_(b)=10`, `N_(a)=5` so that BO =`1/2(10-5)=5/2=2.5`
Again, as it has one unpaired electron in the `pi^(star)(2p_(x))` orbital, therefore, it is paramagnetic.
iv) `N_(2)^(+)` ions `sigma1s^(2), sigma^(star)1s^(2), sigma2s^(2),sigma^(star)2s^(2), pi2p_(x)^(2)=pi2p_(y)^(2)`
Here, `N_(b)=8, N_(a)=4`, Hence, BO`=1/2(8-4)=2`
Presence of no. unpaired electron indicates it to be diaganetic in nature.
As bond dissociation energies are directly proportional to the bond orders, therefore, the dissociation energies of these molecular spcies in the order.
`N_(2)gtN_(2)^(-)=N_(2)^(+)gtN_(2)^(2+)`
As greater than the bond dissociation energy, greater is the stability of these species is also in the above order.