system
Given the following post, respond as if you're commenting on Reddit:
human
Why are there no natural proton emissions in radioactive decay?
gpt
There are nuclides which decay by simply emitting protons, but generally only when the outermost proton(s) are not really bound to the rest of the nucleus. Those nuclides tend to be very proton-rich and have half-lives of fractions of a second, so they're not found in any meaningful amount in nature.

As for less exotic nuclides where the protons are all in bound states, it's just not a competitive decay mode with beta/electron capture or alpha.

For really heavy nuclides, they would prefer to emit alpha particles because alpha particles are very tightly-bound systems, so that's an energetically favorable way to decay.

And for intermediate-mass, proton-rich nuclides, they can just undergo a weak decay (beta-plus or electron capture) over a timescale that's much shorter than waiting for a bound proton to tunnel out.