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Sorry for the very likely ill-posed question. I have lately started reading a lot about quantum physics and the nature of electrons and I read about a phenomenon known as "electron capture" which can happen with a finite probability when an electron "finds" itself within the nucleus volume.

If an electron capture converts a proton and an electron into a neutron plus the emission of an electron neutrino, does this mean that all matter can "decay" with time?

I hope my question is clear enough for someone more expert than me to answer it. Thank you again for your time!

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    $\begingroup$ Electron capture only can happen when energetically favorable. For any stable isotope it isn’t. $\endgroup$ – Jon Custer Sep 2 '19 at 20:26
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    $\begingroup$ Electron capture happens only to atoms whose nuclei have "too many" protons (as compared to the number of neutrons). $\endgroup$ – Thomas Fritsch Sep 2 '19 at 20:34
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The answer to the title question is "sometimes". Some atomic nuclei decay via electron capture, in which case it is at least partially responsible for decay.

The question asks about something else, whether all matter can decay via electron capture. This time the answer is no. Electron capture (like other forms of nuclear decay) can only happen when it's energetically favorable, and for most nuclei this isn't the case.

You can calculate the energy change for a theoretical decay reaction such as

$^{26}_{13}Al + e^{−} \rightarrow ^{26}_{12}Mg$

by summing up the binding energy of the components on the left and comparing them to the nuclei on the right. If it turns out the process needs energy, as opposed to releases it, then it won't happen naturally.

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  • $\begingroup$ Thank you for your answer, it's clear and pointed my in the right direction! $\endgroup$ – Luke Sep 3 '19 at 18:01

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