Question

The paramagnetic behaviour of $B_{2}$ is due to the presence of

• A. $2$ unpaired electrons in $\pi_{b}\, MO$
• B. $2$ unpaired electrons in $\pi^{* }\, MO$
• C. $2$ unpaired electrons in $\sigma^{ *}\, MO$
• D. $2$ unpaired electrons in $\sigma_{b} \, MO$

Answer 1

Answer: (A)

$B _{2}=5+5 =10 e^{-}$
$=\sigma 1 s^{2} \overset{*}{\sigma} 1 s^{2}, \sigma 2 s^{2} \sigma 2 s^{2}, \pi 2 p_{x}^{1}, \pi 2 p_{y}^{1}$
Due to the presence of 2 unpaired electrons, in $\pi$ bonding orbitals, $B _{2}$ shows paramagnetic behaviour.