# If 2s-2p are not mixing

**Question**

Assuming !!2s−2p!! mixing is **NOT** operative, the paramagnetic species among the following is

- !!Be_2!!
- !!B_2!!
- !!C_2!!
- !!N_2!!

**Solution**

The electronic configurations of the given molecules, assuming that !!2s−2p!! mixing is not operative and considering the !!Z-axis!! as the internuclear axis, are as follows:

!!Be_2->!! !! \sigma1s\^2 , \sigma!!*!!1s\^2!!,!!\sigma2s\^2, \sigma!!*!!2s\^2!! (**diamagnetic**)

!!B_2->!! !! \sigma1s\^2!!,!!\sigma!!*!!1s\^2!!,!!\sigma2s\^2 , \sigma!!*!!2s\^2,\sigma2p_z\^2!! (**diamagnetic**)

!!C_2-> \sigma1s\^2!!,!!\sigma!!*!!1s\^2!!,!!\sigma2s\^2, \sigma!!*!!2s\^2,\sigma2p_z\^2,{\pi2p_x^1=\pi2p_y^1}!! (**paramagnetic**)

!!N_2-> \sigma1s\^2 , \sigma!!*!!1s\^2 , \sigma2s\^2, \sigma!!*!!2s\^2,\sigma2p_z^2 ,{\pi2p_x^2=\pi2p_y^2}, {\pi!!*!!2p_x^0=\pi!!*!!2p_y^0},\sigma!!*!!2p_z^0 !! (**diamagnetic**)

Hence, the correct answer is !!C_2!!.

This is a JEE question.