The inertness of the noble gases is due to

Explanation:

Inertiness of the noble gases refers to their lack of reactivity, i.e. the stability provided by a full valence electron shell.

The noble gases are He, Ne, Ar, Kr, Xe, Rd, and, the most recently discovered, Og.

They are located in the last column (18) of the periodic table.

Then, when you do the electron configuration of the noble gases, you find they have the outermost prinicpal energy level full. These are their electron configurations using the abbreviated form:

Being their valence orbitals full, these elements will not be very likely to exchange or share electrons, which is the reason of their inertness.

This does not mean that they do not react at all. Xe and F (the most reactive nonmetal) form some compounds.