system
Given the following post, respond as if you're commenting on Reddit:
human
Why are there no neutrons in a hydrogen nucleus?

I know deuterium and tritium exist, I want to know specifically why the most common form of hydrogen has no neutrons.
gpt
There's an excess of protons and electrons in the universe compared to neutrons, because a free neutron decays to a proton, electron, and neutrinos with a half-life of a little over 10 minutes if it doesn't become part of a nucleus before decaying. Most of those excess protons are in the form of hydrogen (the only nucleus that's stable with no neutrons in it) because most of the universe isn't hot or dense enough to fuse them into anything heavier.