Stability Of Nucleus

• In nature all elements are not stable.
• For example, Oxygen is stable, while Uranium is not.
• Interestingly, Neutron/Proton ratio influences stability.
• There is an optimum ratio needed for a nucleus to be stable and this ratio changes with the
  mass of the nucleus.
• The figure shown below indicates the zone where stable and unstable isotopes lie.
• The ratio of N/P varies from 1-1.5.
• The stable band is shown by a thick line, while the unstable one is shaded.

• The unstable ones emit radiation, transform themselves and move towards stability.
  
• The process of transformation of unstable nucleus by spontaneous emission of radiation is called radioactivity.