Molecular electronic configuration of ${\mathrm{B}}_2$ is

$\mathrm{KK}(\sigma 2 \mathrm{s}{)}^2{\left({\sigma }^{*}2 \mathrm{s}\right)}^2(\pi 2\mathrm{p}{)}_{\mathrm{x}}^2$

$\mathrm{KK}(\sigma 2 \mathrm{s}{)}^2{\left({\sigma }^{*}2 \mathrm{s}\right)}^2(\sigma 2\mathrm{p}{)}^1(\pi 2\mathrm{p}{)}^1$

$\mathrm{KK}(\sigma 2 \mathrm{s}{)}^2{\left({\sigma }^{*}2 \mathrm{s}\right)}^2(\pi 2\mathrm{p}{)}^2$

$\mathrm{KK}(\sigma 2 \mathrm{s}{)}^2{\left({\sigma }^{*}2 \mathrm{s}\right)}^2(\pi 2\mathrm{p}{)}_{\mathrm{x}}^1(\pi 2\mathrm{p}{)}_{\mathrm{y}}^1$