We have a couple of neon lights in my home, and there is one thing I can never figure out. Neon lights are nothing but gas in a tube, and yet they still burn out. First they start blinking and dimming. Then finally they stop working altogether.
How is that possible? How could a gas simply burn out?
I would suspect it’s the electrodes in one or both ends of the tube burning out. The heated electrodes emit metal ions, and eventually the electrode loses enough metal that it burns out the next time you use it.
The main failure mode for neon lamps is deterioration of the electrodes.
So, let’s say you have a heavier than air noble gas, such as xenon. If you could/would use it as a light bulb, would it be possible to replace the electrodes while preserving the gas without contamination that would make it impossible to use?
No, because the gas is necessarily kept at much lower than atmospheric pressure. The reason for this is complex, but suffice it to say, that the lower the gas pressure, the lower the breakdown voltage.