As per molecular orbital theory,the pair of molecules which do not exist is:

The total number of antibonding molecular orbitals,formed from $2s$ and $2p$ atomic orbitals in a diatomic molecule is . . . . . .

The bond order is not $3$ for

The energy of $\sigma 2p_z$ molecular orbital is greater than $\pi 2p_x$ and $\pi 2p_y$ 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 : $N_2, N_2^+, N_2^-, N_2^{2+}$

Explain the structure of the $O_2$ molecule.

In which of the following pairs do the two molecules have identical bond order?