Why does an electron not fall into the nucleus?

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    Electron Fall Nucleus
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Discussion Overview

The discussion centers around the question of why electrons do not fall into atomic nuclei, exploring concepts from quantum physics, classical mechanics, and the nature of atomic structure. Participants examine various theories and interpretations related to electron behavior, energy states, and the implications of quantum mechanics.

Discussion Character

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

Main Points Raised

  • Some participants suggest that the mass and point-like nature of electrons prevent them from falling into the nucleus due to the attractive force of protons.
  • Others argue that electrons are not classical point objects and cannot occupy a lower energy state than the ground state, as described by quantum physics.
  • A participant introduces the uncertainty principle, stating that if an electron were to "fall" into the nucleus, its position would be well-defined, leading to high momentum and the possibility of escaping.
  • Another participant challenges the use of the term "fell," emphasizing that localization of an electron in the nucleus would lead to a superposition of states, including non-bound states, which would likely result in the electron being found elsewhere.
  • Some participants discuss the centripetal force acting on electrons due to protons and draw analogies to planetary motion, questioning whether electrons possess initial momentum that prevents them from moving into the nucleus.
  • It is noted that while the probability density of electrons is not zero in the nucleus, confining an electron to the nucleus would require significant energy, leading it to settle in a lower energy state outside the nucleus.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of electron behavior and the factors preventing them from falling into the nucleus. The discussion remains unresolved, with no consensus reached on the interpretations presented.

Contextual Notes

Some claims depend on interpretations of quantum mechanics and the definitions of energy states, localization, and momentum. The discussion highlights the complexity and nuances involved in understanding atomic structure and electron dynamics.

avito009
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Is it because the electron has less mass and is a point object that prevents it from falling into the nucleus due to attraction of protons?
 
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At the atomic level the electron is not a classical point object which can be thought of as "falling". It is described by quantum physics and it cannot be in a lower energy state than the ground state.
 
I read that

In quantum physics there is something called "the uncertainty principle" that states that we can't know where something is at the same time as we know where it's going (due to it being a wave). Or rather, the better known somethings position is, the less known is it's movement.

Now, with this knowledge we can determine what happens if an electron actually "fell" into the nucleus. The position would be well known (it's in the nucleus), but that means it could be moving really fast, so it breaks free from the nucleus again. This means it can't actually fall in.Why we can't know where something is at the same time as we know where it's going due to it being a wave. How does being a wave effect this?
 
avito009 said:
Now, with this knowledge we can determine what happens if an electron actually "fell" into the nucleus. The position would be well known (it's in the nucleus), but that means it could be moving really fast, so it breaks free from the nucleus again. This means it can't actually fall in.
You need to stop using the word "fell", even within quotes. What you are describing is only a semiclassical and popular interpretation of quantum physics. The point is that if the electron was localised to the nucleus, it would be in a superposition of states which includes several non-bound states as well as some bound states which are bound but not the ground state. The time evolution of the wave function would quickly result in the electron most likely being somewhere else.

avito009 said:
Why we can't know where something is at the same time as we know where it's going due to it being a wave. How does being a wave effect this?
This is also a popular misconception. Particles in quantum physics are not waves, nor are they tiny balls (i.e., classical particles). They have some properties reminiscent of these objects, but they really are quantum particles. The non-localisability of a quantum particle follows directly from the commutation relation between the position and momentum operators.
 
Before going into the millionth near-identical copy of this thread, may I point out that this is the https://www.physicsforums.com/threads/why-dont-electrons-crash-into-the-nucleus-in-atoms.511179/ in the https://www.physicsforums.com/threads/physics-faq-list.807553/ .
 
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I can understand that the electrons orbit the nucleus because there is a centripetal force exerted on the electrons. This centripetal force is due to the attractive force of the protons. But if we observe the Earth which orbits the sun. There is an initial momentum which stops Earth from moving into the sun. Does the electron also have some initial momentum?
 
Vanadium 50 said:
Before going into the millionth near-identical copy of this thread, may I point out that this is the https://www.physicsforums.com/threads/why-dont-electrons-crash-into-the-nucleus-in-atoms.511179/ in the https://www.physicsforums.com/threads/physics-faq-list.807553/ .

That's another topic. This question is not about a loss of energy doe to emission of EM-radiation but about an electron "falling" into the nucleus of an atom. The answer is, that the probability density of the electron is not zero in the nucleus of an atom and for s-electrons it even reaches its maximum in the center. Thus an electron can "fall" into the nucleus and proton-rich nuclei can capture it.
 
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avito009 said:
Does the electron also have some initial momentum?
It is possible for an electron to have an orbital with orbital angular momentum, but there are also orbitals without orbital angular momentum, called s orbitals. Since there are some orbitals without angular momentum, angular momentum is not the thing which prevents the electron from being confined to the nucleus.

In the end, it is just about energy. It would take a lot of energy to confine the electron to the nucleus. So instead it relaxes to a lower energy state where the electron is not confined to the nucleus.
 
Thread locked, pending possible moderation.
 
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After discussion the thread will remain locked and several off topic posts have been removed.
 

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