Why noble gas neon is an unreactive element?

This is because it has a full outer valence shell! so there are 8 electrons and that means it doesn't have the urge the gain anymore

Noble gases already have 8 valence electrons, which means their outermost energy level is completely filled. It doesn't need other elements to react with it. The noble gases are in the last group of the periodic table. Group 1, alkali meatballs, are the most reactive since they carry only 1 valence electrons and need to react with other elements