Question

Use molecular orbital theory to explain why the $B{e}_2$ molecule does not exist.

Answer 1

The electronic configuration of Beryllium is $1s^{2}2s^2.$

The molecular orbital electronic configuration for Be2 molecule can be written as:

Hence, the bond order for $B{e}_2$ is $\frac{1}{2}(N_b-N_a)$

Where,

$N_b$ = Number of electrons in bonding orbitals
$N_a$ = Number of electrons in anti-bonding orbitals

$\therefore$ Bond order of$B{e}_2$ =$\frac{1}{2}(4-4)$ = 0

A negative or zero bond order means that the molecule is unstable. Hence, $B{e}_2$ molecule does not exist.