Why Are Nuclei with Excess Neutrons Unstable?

In summary, the conversation discusses the stability of nuclei with varying numbers of neutrons and protons, and the role of neutron-proton ratio in determining stability. It is explained that nuclei with higher mass numbers have more neutrons than protons because neutrons do not contribute to the coulomb force. However, there is a limit to the number of neutrons that can be bound to a nucleus, which is determined by the short ranged strong force. This is why nuclei with too many neutrons are not stable and undergo beta minus decay. The concept of the neutron drip line is also mentioned as a reference for further reading.
  • #1
Alexitron
14
0
Hi there

First of all excuse my English.

My question is:

Why a nucleus with more neutrons than these in the valley of nuclear stability are not stable
and are beta(-)?

I know that a nucleus with high mass number have more neutrons than protons because the more the protons the higher the coulomb force but neutrons are not charged and can't add coulomb force in the nucleus.
So why Ge(32P,41N) is more stable than it's isotope Ge(32P,46N)
(which by the way has p&N even) ?

Thanks in advance.
 
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  • #2
Because the most favorable configuration is Ge(32P,41N) : you see, with your logic, Ge(32P,1187455N) would be more stable than Ge(32P,955N), and so on.

Neutrons are only 'feeling' the short ranged strong force, so there exists an upper limit for the number of neutrons a nuclei with a certain number of protons can bind. You can't just pack an arbitrary number of neutrons to a nucleus and make it stable. You can google for instance "neutron drip line" and read about it.

cheers
 
  • #3


Hello,

Thank you for your question. The "valley of nuclear stability" refers to the region in the chart of nuclides where stable nuclei are found. This means that the nucleus has a balanced number of protons and neutrons, leading to a more stable configuration.

As you mentioned, the coulomb force between protons can contribute to instability in a nucleus with a higher number of protons. However, it is not the only factor that affects stability. The ratio of protons to neutrons also plays a significant role. Too many or too few neutrons can disrupt the delicate balance of forces within the nucleus, leading to instability.

In the case of Ge(32P,41N) and Ge(32P,46N), the difference in stability can be attributed to the ratio of protons to neutrons. While both have the same number of protons, the isotope with 46 neutrons has a higher neutron-to-proton ratio, making it less stable.

I hope this helps to answer your question. Thank you for your interest in nuclear stability.
 

1. What is the Valley of Nuclear Stability?

The Valley of Nuclear Stability is a concept in nuclear physics that refers to the region on a chart of nuclides where the majority of stable, naturally occurring isotopes are located. It is also known as the "belt of stability."

2. How is the Valley of Nuclear Stability determined?

The Valley of Nuclear Stability is determined by plotting the number of protons against the number of neutrons for all known isotopes. The most stable isotopes are located closest to the line of stability, which runs diagonally from the upper left to the lower right of the chart.

3. What factors influence the stability of a nucleus?

The stability of a nucleus is influenced by the balance between the strong nuclear force, which holds the nucleus together, and the electromagnetic force, which repels protons from each other. The number of protons and neutrons, as well as their arrangement, also play a role in the stability of a nucleus.

4. Why is the Valley of Nuclear Stability important?

The Valley of Nuclear Stability is important because it helps scientists understand and predict the stability of different isotopes and their likelihood of undergoing radioactive decay. It also helps guide the production of stable isotopes for various industrial and medical purposes.

5. Are there any exceptions to the Valley of Nuclear Stability?

Yes, there are some exceptions to the Valley of Nuclear Stability. Some isotopes that are located outside of the valley may still be considered stable due to their extremely long half-lives. Additionally, there are some isotopes that are located within the valley but are still unstable and undergo radioactive decay. These exceptions are due to complex interactions between the strong nuclear force and other factors.

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