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Updated December 14, 2021
  Valley of stability

Image: The valley of isotope stability by type of radioactive decay.
- In black: stable nuclei, they do not undergo radioactive decay and do not emit radiation.
- In orange, blue and yellow: unstable nuclei which disintegrate either by radioactivity β either by radioactivity α to descend into the valley.
- In red and purple: unstable nuclei which have too many protons or neutrons emit either a proton or a neutron to descend into the valley.
- In pale green: unstable nuclei which have too many protons and neutrons must crack in order to descend into the valley.
We can notice that for Z<20, the set of stable nuclei lie on the bisector N = Z.
For Z>20, the set of stable nuclei lie above the line N = Z in the valley of stability. Nuclei must integrate more and more neutrons than protons as they grow larger.
For Z>83, there are no more stable nuclei despite observable limit of the number of protons which is estimated at around Z=126.
The unstable nuclei undergo a cascade of radioactive decays to ultimately throw themselves into the river of stable matter flowing at the bottom of the valley.

 
           
           
   
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