Why extra neutrons make the nucleus unstable?

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    Neutrons Nucleus
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Discussion Overview

The discussion revolves around the stability of atomic nuclei in relation to the number of neutrons present. Participants explore the relationship between the neutron-to-proton ratio and nuclear stability, considering theoretical and conceptual aspects of nuclear forces and decay processes.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why additional neutrons, which contribute to the strong nuclear force, lead to instability despite the expectation that more strong force would provide more stability.
  • Another participant suggests that excess neutrons can alter the shape of the nucleus, potentially leading to instability due to small disturbances.
  • A different viewpoint highlights the Pauli exclusion principle, explaining that as more neutrons are added, they occupy higher energy states, which may lead to instability and processes such as beta decay or neutron emission.
  • There is a mention of the inherent instability of free neutrons, prompting consideration of their stability within the nucleus.

Areas of Agreement / Disagreement

Participants express various hypotheses regarding the role of neutrons in nuclear stability, indicating that multiple competing views remain without a consensus on the exact mechanisms leading to instability.

Contextual Notes

Some assumptions regarding the nature of nuclear forces, the specific conditions under which instability occurs, and the implications of the Pauli exclusion principle are not fully explored or resolved.

skepticwulf
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I understand that having neutrons in nuclei creates additional strong nuclear force which brings protons together, overcoming EM force thus forming different atoms but why extra neutrons bring instability? Wouldn't more strong force mean extra "glue" to hold nuclei together? yet it seems N/P ratio is best at 1/1, why??
 
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There are several ways large numbers of neutrons lead to instabilities - i.e. the extra neutrons could cause the shape of the nucleus into an unstable configuration so small disturbances make it, basically, shake itself to bits.

You realize that neutrons are, themselves, unstable? So think about why they are apparently stable while inside a nucleus.
 
Thank you.
I understand by your reply as well as by similar discussions.
 
The Pauli exclusion principle is relevant here. Neutrons are fermions - no two neutrons can occupy the same state. If you add more and more neutrons, they have to use states with increasing energy - at some point this makes the nucleus instable against beta decay (a neutron converts to a proton and emits electron+neutrino) or even direct emission of a neutron. Fission of the whole nucleus can get possible as well.
 
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