How can you predict nuclear stability?

1 Answer
Mar 21, 2014

Most nuclei are stable if the neutron-to- proton ratio is between 1 and 1.5 and the total number of nucleons is less than 209.

NEUTRON/PROTON RATIO

At close distances, a strong nuclear force exists between nucleons. This attractive force comes from the neutrons. More protons in the nucleus need more neutrons to bind the nucleus together.

The graph below is a plot of the number of neutrons versus the number of protons in various stable isotopes.

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The stable nuclei are in the pink band known as the belt of stability. They have a neutron/proton ratio between 1:1 and 1.5:1.

NUMBER OF NUCLEONS

The nuclear strong force operates over only short distances. When a nucleus is too big, the strong force is no longer able to hold the nucleus together. After 83-bismuth-209, all nuclei are unstable.