Assuming that Hund's rule is violated, the bond order and magnetic nature of the diatomic molecule B₂ is

Hund's rule of maximum multiplicity states that if two orbitals are of the same energy, then pairing in orbitals is performed only after the two orbitals are half-filled. Total number of electrons in B₂ is 10 .Molecular orbit electronic configuration of B₂ (when no rule is violated).

$\left(\sigma 1s^2\right)\left(\sigma *1s^2\right)\left(\sigma 2s^2\right)\left(\sigma *2s^2\right)\left(\pi 2p_y^1=\pi 2p_x^1\right)$

Molecular orbital electronic configuration when Hund's rule is violated.

$\left(\sigma 1s^2\right)\left({\sigma }^{\ast }1s^2\right)\left(\sigma 2s^2\right)\left({\sigma }^{\ast }2s^2\right)\left(\pi 2p_x^2=\pi 2p_y^0\right)$

According to the above electronic configuration, B₂ is diamagnetic. Bond order of B₂ is:

$\begin{array}{ccc}\mathrm{Bond} \mathrm{order}& =& \frac{6-4}{2}\\ & =& 1\end{array}$