Answer:
The noble gases are stable because their outermost (valence) shell of electrons is full.
Step-by-step explanation:
The noble gases are stable because their outermost (valence) shell of electrons is full. This statement is true and it makes them unreactive due to the presence of complete electron in their outermost shell. Since their outermost electrons is complete, they cannot share their electrons to other atoms as such they won't be able to react with other atoms.