Alpha Decay

Alpha particle contains 2 protons and 2 neutrons.  Radioactive material emits alpha particle and the process is called alpha decay.  In order to unfetter from the strong nuclear forces that holds the nucleon together, the alpha particle must attain sufficient energy to get pass the Coulomb barrier.  Alpha particle could not attain such energy.  They escapes from the nucleus using quantum tunneling.  Alpha particle's wave function has increasing probability to be found outside the nucleus as time goes by.  The wave function matches the observation of half life for radioactive substances