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RobusEtCeleritas t1_j5awcof wrote

Free neutrons decay with a half-life of about 15 minutes. But that doesn't apply to neutrons bound inside of nuclei.

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InTheEndEntropyWins t1_j5ay08s wrote

Why is the half-life different when a neutron bound in a nuclei?

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louiswins t1_j5bazp5 wrote

A free neutron can decay because its mass-energy is greater than that of the resulting particles, proton + electron + antineutrino (and because it meets a few other conditions). But the binding energy that keeps a neutron in a nucleus is negative (and therefore the mass of a nucleus is less than the sum of the masses of its constituent protons & neutrons). If the neutron decayed it would violate conservation of energy, and therefore it must be stable.

However, in some neuclei the energies work out such that a neutron can still decay! We call those radioactive isotopes. For example ^(14)C decays into ^(14)N by emitting an electron+antineutrino and changing one of its neutrons to a proton - sound familiar?

Matt Strassler has a good article on exactly this topic, which also links to his articles about particle decay in general: https://profmattstrassler.com/articles-and-posts/particle-physics-basics/mass-energy-matter-etc/the-energy-that-holds-things-together/neutron-stability-in-atomic-nuclei/

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