Chemistry – The Periodic Table - Noble gases | e-Consult

The noble gases are typically monoatomic gases because their unreactivity is linked to their stable, filled valence shells. Achieving a stable octet means they have no need to form chemical bonds with other atoms. Chemical bonds typically involve the sharing or transfer of electrons to achieve a full valence shell. Since noble gases already have a full valence shell, there is no benefit to forming a bond.

To form a diatomic molecule, for example, a noble gas would need to gain or lose electrons to achieve a full octet. However, this would disrupt their already stable electronic configuration. Therefore, they exist as individual, independent atoms – hence, monoatomic gases. The stability conferred by their full valence shells makes the energy required to form a bond energetically unfavourable.