system
Given the following post, respond as if you're commenting on Reddit:
human
Why is tritium radioactive, even though it's nucleus is not dense at all?

I thought the reason elements were radioactive were because their nuclei was too dense to be stable, so to become stable it ejects particles in the form of alpha/beta particles and energy in the form of gamma rays.

Tritium has a measly proton+2 neutrons. Why is it radioactive?
gpt
Radioactivity doesn't depend on density.  It depends on stability of the nucleus (which does depend on density a bit but there are other factors).  Basically can the neutrons and protons stay bonded together.  If they can't, then some form of decay will occur to make it more stable.  Tritium is not as stable as He-3, so the neutron decays into a proton in order for the system to reach a stable arrangement.