Question

Li2 molecule exists whereas be2 molecule does not exist explain why

Answer 1

Answer

The electronic configuration of Beryllium is 1s2 2s2.  

From the electronic configuration it is clear that there is no singly filled atomic orbital present in beryllium.

Without the half filled orbital,the overlapping is not possible ,therefore Be2 molecule does not exist.

Answer 2

Li$_{2}$ molecule exists whereas Be$_{2}$ molecule does not exist .

The existence of a molecule can be predicted by knowledge of molecular orbital theory ( MOT ) . The molecule having bond order more than zero may exist .

The bond order of Li$_{2}$ molecule is 1 . So it exists .

But the bond order of Be$_{2}$ molecule is 0 ( zero ) . So it can not exist .