# Why is octet extra stable? [duplicate]

In chemistry, it is agreed in general that the octet is extremely stable, through experiments except in some cases. But is there any specific theoretical reasoning for that?

According to me, if:

1. The $\ce{s}$ and $\ce{p}$ orbitals are full, they should repel in every orbital, causing destabilization.
2. There is no exchange of energy in fully-filled orbitals as it occurs in half filled orbitals.

So, shouldn't these two reasons make an octet filled atom unstable? Then, why is the octet stable and how does it counter the above arguments?