question_answer 1)

Use molecular orbital theory to explain why the \[B{{e}_{2}}\] molecule does not exist?

Answer:

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.