Question

Why are the Noble Gases unreactive?

Answer 1

Because they contain a full valence shell of electrons.

Explanation:

Noble gases contain a full valence of electrons. Because of this configuration, they are (i) difficult to reduce (electrons must enter the next valence shell), and (ii) difficult to oxidize, the valence electrons are tightly held by the nuclear charge.

Of course, some compounds of the Noble Gases do exist, usually with highly the highly oxidizing elements, oxygen and fluorine.