Why does an atom that decays by emitting alpha or beta radiation become an atom of a different element?

Alpha radiation is when the nucleus of an unstable element releases an alpha particle (two protons and two neutrons; the equivalent of the nucleus of a helium atom)due to the weak nuclear force. The resulting atom is now a different element because the number of protons it has determines which element it is. Beta radiation (β− ) is when a neutron in an unstable atom with an excess of neutrons turns into a proton because of a virtual W− boson, one of the particles that carries the weak force. This boson then decays into an electron and an electron type antineutrino. Another type of beta radiation (β+ ) is the same as the previous type except that a proton decays into a neutron and a W+ boson decays into a positron (electron antiparticle) and an electron type neutrino instead. Beta radiation changes the number of protons in a nucleus and therefore the type of element.