Chemists have revealed that $1 \lambda^{2}, 2 \lambda^{2}$ -disilene $\left(\mathrm{Si}_{2}\right)$ is diamagnetic while disulfur $\left(\mathrm{S}_{2}\right)$ is paramagnetic $(\mathrm{S}=1)$. Draw the MO diagram (valence shell only), determine the bond order for those two molecules and conjecture which element has higher $3 \mathrm{~s}-3 \mathrm{p}$ energy gap. (Note that $\sigma_{\mathrm{g} 3 \mathrm{pz}}$ is lower-lying than $\pi_{\mathrm{u} 3 \mathrm{p}}$ in $\mathrm{S}_{2} .$ )
It seems that the paramagnetic type is not very necessary - however, I couldn't come up with the correct MO diagram in either case.
