Proton decay mode prediction using

Sometimes it is difficult to predict if a particular isotope is stable and, if unstable, what type of decay mode it might undergo. All isotopes that contain 84 or more protons are unstable. These unstable isotopes will undergo nuclear decay. For these large massive isotopes, we observe alpha decay most commonly. Alpha decay gets rid of four units of mass and two units of charge, thus helping to relieve the repulsive stress found in the nucleus of these isotopes. For other isotopes of atomic number less than 83, we can best predict stability by the use of the neutron to proton (n/p) ratio. 

A plot of the neutrons (n) versus the protons (p) for the known stable isotopes gives the nuclear belt of stability. (See your textbook for a figure of the belt of stability.) At the low end of this belt of stability (Z < 20), the n/p ratio is 1. At the high end (Z 80), the n/p ratio is about 1.5. We can then use the n/p ratio of the isotope to predict if it will be stable. If it is unstable, then the isotope will utilize a decay mode that will bring it back onto the belt of stability. 

The pattern of nuclear stability can be used to predict the likely mode of radioactive decay neutron-rich nuclei tend to reduce their neutron count proton-rich nuclei tend to reduce their proton count. In general, only heavy nuclides emit a particles. 

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