The chemical properties of noble gases are not terribly interesting. That’s because noble gases have what is called a filled valence shell. The science of quantum mechanics explains how electrons build up in different energy levels. These energy levels are more stable when filled than when empty. This makes sense on an intuitive level. After all, something that is filled cannot have anything added to it and therefore it is harder to change. That’s what stable means- resistant to change.
Noble gases have the right number of electrons in their outer shell. That’s why they do not tend to react with other types of atoms, since they do not need to gain or lose an electron in order to have that magic number. No one knows exactly why the number work out the way they do. Theoretical chemists can do all kinds of calculations, but those are simply using math to back-rationalize what is observed in nature. The fact is that certain numbers of electrons are stable, while others aren’t.
Because noble gases are so stable, they are monatomic gases. This is in sharp contrast to less stable elements like bromine, chlorine, fluorine, iodine, and oxygen. These elements do not exist as individual atoms, but as pairs, diatoms. When in the gas state, this pair is the molecular unit. Noble gases, on the other hand, are truly in their free atomic form when in their elemental state. They do not even react with themselves. That shows how extraordinarily stable they are.
The element fluorine is very reactive. My chemistry professor in college quipped that you can recognize fluorine chemists because they are missing fingers! This morbid sentiment refers to the fact that fluorine will react with just about anything, and can cause fires, explosions, and lung damage from inhalation.
Because fluorine is so reactive, it forms compounds with some of the noble gases. In fact, to store fluorine, it is often reacted with xenon. The product of that reaction is stored in a cylinder, and when it is opened, fluorine is released. This happens because the generally unreactive xenon would rather be by itself than be reacted with fluorine. In essence, it kicks fluorine out in order to maintain it’s magic number of electrons and its filled outer shell.