How does electron capture change an atom’s atomic number?

During the process of electron capture, an atom’s atomic number decreases by one unit.1

In this form of radioactive decay, the nucleus captures an orbital electron from the surrounding electron cloud. This interaction transforms the parent nucleus into a daughter nucleus with one fewer proton, effectively changing the identity of the chemical element. For example, when a nucleus of beryllium-7 captures an inner electron, it decays into lithium-7. As the vacancy in the electron cloud is filled by another electron, the atom typically emits an X-ray.1