• # question_answer39) Use molecular orbital theory to explain why the $B{{e}_{2}}$ molecule does not exist?

Electronic configuration of Be-atom = $1{{s}^{2}},2{{s}^{2}}$ M.O. electronic configuration of $B{{e}_{2}}$ Compare the relative stabilities of the following species $=\sigma {{(1s)}^{2}}\overset{*}{\mathop{\sigma }}\,{{(1s)}^{2}}\sigma {{(2s)}^{2}}\overset{*}{\mathop{\sigma }}\,{{(2s)}^{2}}$ $\therefore$ Bond order $=\frac{1}{2}(4-4)=0$ Hence, $B{{e}_{2}}$does not exist.