Disintegration type of some radionuclides, e.g. K-40, Mn-54, Fe-55. The nucleus of an atom captures an electron of the atomic shell, whereby a proton in the nucleus converts into a neutron. The formed nuclide has an atomic number which is smaller by one unit; the mass number remains the same. Example: K-40 + e- => Ar-40.

Electron capture; capture of an electron from the nuclear shell of the electron sheath during the disintegration of potassium-40 into argon-40