Source
r/askscience•
Tenthyr

In a universe with Electrons, how stable are nuclei?

Physics

EDIT: damn you autocorrect! A universe WITHOUT electrons!

Nuclei are held together by the residual strong force, yes. But in a universe that has, for mysterious magic reasons, become devoid of electrons, would nuclei remain as stable as they would have with orbiting electrons?

I know that the nucleus basically has no baring on the chemical interactions of its electron shells, but do the electron shells have no baring on the nuclei system too?

Posted Sep 15, 2016, 3:45 PM UTC

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RobusEtCeleritasExperimental Nuclear Physics•

The nucleus doesn't really care about what's going on at the atomic level. The exceptions would be decays via electron capture or internal conversion.

Other than that, the electron cloud plays basically no role in the structure and behavior of the nucleus.

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hikaruzero•

Other than that, the electron cloud plays basically no role in the structure and behavior of the nucleus.

He he ... can we really say that for sure, now that we know more about the proton radius puzzle? Gonna be real interesting to see how that pans out ... !

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RobusEtCeleritasExperimental Nuclear Physics•

I don't see how that's related.

2
hikaruzero•

Uh, you don't? Surely you're aware of everything discussed in this article, yes?

Measurements of the radius of a proton in two isotopes of hydrogen (protium and deuterium) suggest that the proton has a different radius depending on whether it is bound to an electron, or to a muon. The standard model suggests that the proton should interact with both the same way, however several experiments currently disagree with this prediction. Among the proposals to resolve this include hypotheses such as electrophobic forces where the nucleus interacts with electrons differently than muons. This hypothesis at least would clearly necessitate that the presence of electrons plays some role in the structure and behavior of the nucleus.

No?

1
RobusEtCeleritasExperimental Nuclear Physics•

This is more directly related to atomic structure than nuclear structure, the small connection being the nuclear charge radius.

The nucleus involved is the deuteron, which is very important in understanding nuclear structure, but it's by no means representative of a typical nucleus. The deuteron is the most weakly-bound nucleus in existence.

So when you take the most weakly-bound nucleus and subject it to extreme conditions (atomic muons instead of electrons) you notice some slight effect on nuclear structure.

The proton radius puzzle is interesting, but not really nuclear structure if you ask me.

As far as most electron clouds are concerned, the nucleus is pointlike. The effects of the internal structure of nuclei on atomic structure are small (hyperfine structure, isotopic shift, etc.), and the effects of the atomic structure on nuclear structure are effectively nil.

5
iorgfeflkdBiophysics•

There are a few decay processes, mainly electron capture, that involve shell electrons interacting with the nucleus to induce decay. This would not happen without electrons. However, in your scenario, what happens when an unstable nucleus undergoes beta decay?

3
TenthyrOP•

My hypothetical is a bit rediculous. It was really I guess just a way of setting up the question 'does the nucleus exist the same amount of time it would have with electrons if it was kept without them.

1
Mysunsai•

I'm unsure what you mean by that last part. Electron shells do not exhibit chemical interactions, only electromagnetic interactions. What we term "chemical" are an emergent property of the electronic interactions between the electron clouds of multiple atoms, not a "real" unique type of interaction. And in both cases, the nuclei plays a very large role. Charge density is the defining factor in chemical reaction theory, and as the nucleus is the only source of positive charge... And as far as the electron shells, without the nuclei the only interaction would be for every electron to get as far away from each other as possible.

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TenthyrOP•

All chemical reactions are between the valence electrons of atoms and basically are independent of any nuclear influennce in the sense the nucleus itself will not interact chemically in any way.

1
Mysunsai•

The electrons also do not react "chemically" in any way. They only interact electro dynamically. Chemical reactions are a classification that only atoms and molecules can undergo. Valence electron theory is one very simple method of analyzing chemical reactions. It relays on atomic orbital theory. Atomic orbital theory takes the known orbitals of a hydrogen atom, and assumes that all atoms have identical orbitals. The orbitals themselves are defined based on solutions to minimize the electrodynamic interaction energy between the nucleus and the electrons.

The nuclei are an integral part of chemical bonds. If only the electrons interacted, then you'd have two clouds of negative charges in a small space. Those negative charges would attempt to get as far away from each other as possible. So no atoms would ever get near each other. The reason they do get near each other is that the electrons are attracted to the nuclei. If their electron configurations are complementary, that attraction can cause electrons to preferentially congregate in between the two nuclei, thereby holding two atoms together through the charge attraction between the nuclei and the electrons.

If you don't like that answer, then just consider what it means when Na+ interacts with Cl-. Because there are definitely no positrons floating around creating a positive charge. Only protons in the nucleus.

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TenthyrOP•

You're being aggressively pedantic. Chemical interactions are the result of interactions of different atoms valence electors. Yes, a nucleus is required for electrons to be in their orbitals to actually result in chemical interactions of atoms, but the nucleus foes not itself take part in those interactions. Isotopes can react just like their stable relatives, ignoring the effects of decay.

I am not arguing that chemical reactions do not require atoms, and I'm not sure where you got that. I am saying that chemistry itself occurs with no Imput from the nucleus at all in regards to reactions and bonding. Electromagnetism results in atoms, but the residual strong force has no effect on electrons at all. Meanwhile (and this is what I asked the question to confirm) the forces that result in electron clouds have no real bring on the stability of the nucleus barring electron capture and decay.

1
Mysunsai•

Ok. I guess I was just assuming from your question that you were interested in a quantum mechanical understanding of atomic theory. I admit that I'm probably not the best at simplifying the subject if people don't already have some background. It's just that valence electron theory is a very simplified explanation of the system which strips out most of the bits that would be relevant to your question.

But yes, in general nuclei in isolation remain relatively stable without electrons. We know this is true for low mass nuclei, as we can actually ionize them to a zero electron state. It's probably still true for other nuclei, but it takes so much energy to ionize them that we can't test it.

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