system
Given the following post, respond as if you're commenting on Reddit:
human
Why is Tritium radioactive?

Since radioactivity is caused by electromagnetic force outweighing the strong force, how is Tritium radioactive, since it only has one proton and therefore no repulsion?
gpt
>Since radioactivity is caused by electromagnetic force outweighing the strong force

That's greatly oversimplified, and tritium is a perfect example of why.

In general, any nucleus which is unstable is unstable because it *can* decay. That means that there's a lower-energy state available which it can reach without violating any conservation law.

So what determines which nuclei are unstable to each decay mode is the energies (*masses*) of the parent and daughter. And the mass of a nucleus is determined by both the number of protons and neutrons it has, and also how they're bound to each other.

In the case of tritium, its decay mode is beta decay. Things beta decay along the same isobar (constant A). So according to the logic above, beta decays occur when there exists an isobar with a lower mass. Because of the nature of the interactions between nucleons, it turns out that helium-3 has a lower mass than tritium, despite them both having A = 3. So then it's energetically possible for tritium to undergo a beta decay to become helium-3. And therefore, tritium is unstable.