Question

What does the weak nuclear force in the atom do?

Answer 1

In particle physics, the weak interaction (the weak force or weak nuclear force) is the mechanism of interaction between sub-atomic particles that causes radioactive decay and thus plays an essential role in nuclear fission.
Beta decay is just one example of the weak force. During beta decay a neutron disappears and is replaced by a proton, an electron and a neutrino (anti-electron)