Why noble gases are called inert gases?

Noble gases:

1. Noble gases are the elements that have completely filled the valence shells i.e. their octets are completed.
2. Noble gases are Helium $\mathbf{\left(}\mathbf{He}\mathbf{\right)}$, Neon $\mathbf{\left(}\mathbf{Ne}\mathbf{\right)}$, Argon $\mathbf{\left(}\mathbf{Ar}\mathbf{\right)}$, Krypton $\mathbf{\left(}\mathbf{Kr}\mathbf{\right)}$, Xenon $\mathbf{\left(}\mathbf{Xe}\mathbf{\right)}$ and Radon $\mathbf{\left(}\mathbf{Rn}\mathbf{\right)}$.
3. As the valence shells of noble gases are completely filled, they do not combine with other elements to form compounds.
4. Thus, noble gases are chemically unreactive.
5. Thus. noble gases are known as inert gases because of their reluctance to combine with other elements to form compounds.