Use molecular orbital theory to explain why the $Be_{2}$ molecule does not exist.

(N/A) The electronic configuration of Beryllium $(Be)$ is $1s^{2} \, 2s^{2}$.
The molecular orbital electronic configuration for the $Be_{2}$ molecule is:
$\sigma_{1s}^2 \, \sigma_{1s}^{*2} \, \sigma_{2s}^2 \, \sigma_{2s}^{*2}$.
The bond order is calculated using the formula: $\text{Bond Order} = \frac{1}{2}(N_{b} - N_{a})$.
Here,$N_{b}$ is the number of electrons in bonding molecular orbitals and $N_{a}$ is the number of electrons in anti-bonding molecular orbitals.
For $Be_{2}$,$N_{b} = 4$ and $N_{a} = 4$.
$\therefore \text{Bond Order} = \frac{1}{2}(4 - 4) = 0$.
$A$ bond order of $0$ indicates that the molecule is unstable and does not exist.