Does weak nuclear force cause radioactivity?
The weak nuclear force is responsible for only the beta decay form of radioactivity.
There are three forms of radioactivity, alpha, beta and gamma.
Alpha decay only occurs in heavier elements which give up energy when the nucleus is divided. An alpha particle is a Helium nucleus consisting of two protons and two neutrons. Unstable nuclei can emit an alpha particle by a quantum tunnelling effect which enables the repulsive electromagnetic force to overcome the strong nuclear force.
Beta decay is where a neutron turns into a proton by emitting an electron or a proton turns into a neutron by emitting a positron. Actually as a proton consists of two up quarks and a down quark and a neutron consists of two down quarks and an up quark, beta decay involves turning an up quark into a down quark or vice versa.
The weak nuclear force is mediated by the W bosons. To turn a neutron into a proton:
Gamma decay normally happens after alpha or beta decay when the nucleus is in an excited state. A high energy photon, a gamma ray, is emitted to return the nucleus to its ground state.