In alpha decay, an atomic nucleus emits an alpha particle (identical to a helium-4 nucleus). This happens in large nuclei because the nuclear force keeping the nucleus together is outweighed by the electromagnetic force.

Makes sense to me, but isn't the weak interaction supposed to be "responsible for all radioactive decay of atoms"? Alpha decay is considered as such, so is the weak interaction involved in any way?

  • $\begingroup$ Do you have a reference for the weak interaction supposedly being "responsible for all radioactive decay of atoms"? Admittedly, most introductory material on the nuclear forces concentrates on the strong force and is pretty vague about the role of the weak force, just mumbling something about it being responsible for radioactive decay. $\endgroup$
    – PM 2Ring
    Jan 18, 2021 at 2:03
  • $\begingroup$ Well, I know you're not supposed to trust everything on the internet, but en.wikipedia.org/wiki/Weak_interaction says "responsible for the radioactive decay of atoms", which I interpret as meaning all of it (because of the the definite article). $\endgroup$
    – David Cian
    Jan 18, 2021 at 18:06
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    $\begingroup$ Fair enough. That Wikipedia sentence is slightly misleading, but the article does go on to clarify that statement. The weak force is responsible for changing the flavor of quarks & leptons, so it's very important in beta decay, but of less importance in other decays, although all 3 forces contribute in some fashion to every decay, as Thomas's answer mentions. You may enjoy this related question: physics.stackexchange.com/q/562319/123208 $\endgroup$
    – PM 2Ring
    Jan 18, 2021 at 18:36
  • $\begingroup$ Also related: physics.stackexchange.com/q/261473/123208 & physics.stackexchange.com/q/488007/123208 $\endgroup$
    – PM 2Ring
    Jan 18, 2021 at 18:51

1 Answer 1


The basic radioactive decay modes are alpha decay (the emission of a helium nucleus), beta decay (the emission of electrons/positrons and neutrinos), and gamma decay (emission of photons). These decays are governed by the strong, weak, and electromagnetic force, respectively.

Obviously, there are many details. There are other forms of radioactivity (neutron emitters, proton emitters, .. ), and all interactions contribute to the precise rate of alpha, beta, and gamma decays. For example, since alphas are charged, the alpha decay rate is governed by the Coulomb barrier.

  • 2
    $\begingroup$ Given that the alpha particle is charged, electromagnetism must play some role, right..? $\endgroup$
    – kaylimekay
    Jan 18, 2021 at 1:48
  • $\begingroup$ @kaylimekay Fair point, but Thomas is just giving a simplified overview. Hopefully, it's not too simplified. ;) $\endgroup$
    – PM 2Ring
    Jan 18, 2021 at 1:56
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    $\begingroup$ @kaylimekay added a short postscript $\endgroup$
    – Thomas
    Jan 18, 2021 at 2:27

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