As another not-physicist who is interested in physics, I've found the articles/explainers at Of Particular Significance very helpful. There are a few on particl

As another not-physicist who is interested in physics, I've found the articles/explainers at Of Particular Significance very helpful. There are a few on particle decay, and I think that these two provide a longer answer to your questions: Most Particles Decay — But Why? https://profmattstrassler.com/articles-and-posts/particle-physics-basics/why-do-particles-decay/most-particles-decay-why/ https://profmattstrassler.com/articles-and-posts/particle-ph... Most Particles Decay — Yet Some Don’t! https://profmattstrassler.com/articles-and-posts/particle-physics-basics/why-do-particles-decay/most-particles-decay-yet-some-dont/ https://profmattstrassler.com/articles-and-posts/particle-ph... Neutron Stability in Atomic Nuclei https://profmattstrassler.com/articles-and-posts/particle-physics-basics/mass-energy-matter-etc/the-energy-that-holds-things-together/neutron-stability-in-atomic-nuclei/ https://profmattstrassler.com/articles-and-posts/particle-ph...