Why don't electrons fall into the nucleus?.

[francis20520]

TL;DR

Why don't electrons crash into the nucleus or fly away from it?

The first result to this question in Google gives this: "An electron in an atom spreads out according to its energy. The states with more energy are more spread out. All electron states overlap with the nucleus, so the concept of an electron "falling into" or "entering" the nucleus does not really make sense. Electrons are always partially in the nucleus " - https://wtamu.edu/~cbaird/sq/2013/08/08/why-dont-electrons-in-the-atom-enter-the-nucleus/

However as a layman this raises questions like this:
(1.) Then how come you can isolate single electrons and create an electron beam. For example, in the double slit experiment, they fire single electrons. The electron beam has only electrons. It has no nucleus. So how come isolated electrons can exist?

(2.) Atoms exchange electrons like in chemical and nuclear reactions. For example Ionic bonding is the complete transfer of valence electron(s) between atoms.

How can this happen?? Because if an electron is just an extension of a nucleus then how can electrons be exchanged between two different nuclei?

 

[fresh_42]

It occurs and is one of the many decay channels of radioactivity. A nucleus can capture one or two electrons or emit positrons and neutrinos.
https://en.wikipedia.org/wiki/Beta_decay#β+_decay_and_electron_capture
https://en.wikipedia.org/wiki/Electron_capture

 

[Dale]

how come you can isolate single electrons and create an electron beam.

Notice that the quote said "An electron in an atom ". You create an electron beam by removing the electrons from the atom so that they no longer qualify as an electron in an atom.

if an electron is just an extension of a nucleus then how can electrons be exchanged between two different nuclei?

The quote never claimed that an electron is just an extension of a nucleus. It merely said that an electron in an atom is partially in the nucleus. When an electron moves from one atom to another it changes which nucleus it is partially in. In a covalent bond the electron is partially in both nucleii (I believe).

 

[PeroK]

Summary:: Why don't electrons crash into the nucleus or fly away from it?

The first result to this question in Google gives this: "An electron in an atom spreads out according to its energy. The states with more energy are more spread out. All electron states overlap with the nucleus, so the concept of an electron "falling into" or "entering" the nucleus does not really make sense. Electrons are always partially in the nucleus " - https://wtamu.edu/~cbaird/sq/2013/08/08/why-dont-electrons-in-the-atom-enter-the-nucleus/

However as a layman this raises questions like this:
(1.) Then how come you can isolate single electrons and create an electron beam. For example, in the double slit experiment, they fire single electrons. The electron beam has only electrons. It has no nucleus. So how come isolated electrons can exist?

(2.) Atoms exchange electrons like in chemical and nuclear reactions. For example Ionic bonding is the complete transfer of valence electron(s) between atoms.

How can this happen?? Because if an electron is just an extension of a nucleus then how can electrons be exchanged between two different nuclei?

An electron in an atom is part of a so-called bound state. This is analogous to the planets being in bound states orbitting the Sun. At the atomic level, however, bound states are fundamentally different from planetary bound states. This is why the "mini solar system" model of the atom is not valid.

Instead, the electron may only occupy certain energy levels (this is analogous to planets being limited to certain defined orbits) - but, when the electron is in a defined bound state energy level it has no definite position. This is at the heart of QM and the uncertainty principle: if the electron has a well-defined energy, then it does not have a well-defined position.

In that sense the electron is spread out. Although, I think it is far better to say that the question of where the electron is has no meaning. It's not anywhere really.

It doesn't fall into the nucleus because that has no real meaning in QM. It's not in a orbit with a position, velocity and a trajectory. It's in an energy state with no classical analogue. This model of the atom describes how the electron behaves under the electromagnetic interaction with the nucleus.

If a photon interacts with an atom, it can give an electron enough energy to escape its bound state. It then behaves as a free electron. Although still subject to quantum uncertainty it may now behave as a free wave-packet, which is the QM equivalent of a classical particle in motion.

The process of electron capture is more complicated and involes the weak interaction between the electron and the nucleus:

https://en.wikipedia.org/wiki/Electron_capture

 

[Helena Wells]

Electrons are quantum objects they do not have a definite position until you measure them. Because the are quantum objects they obey the Schrödinger equation.They interfere with thenlmselves.If you apply the Schrödinger equation for any chemical element according to the Born rule there is a 0% probability of finding them at the nucleus.

 

[Vanadium 50]

.If you apply the Schrödinger equation for any chemical element according to the Born rule there is a 0% probability of finding them at the nucleus.

That is not true. There is a small probability the electron is in the nucleus. (Of order a few parts per million) But so what? Most of the time it just flies out again. Rarely it initiates a weak transition, as mentioned in post #2.

One cannot completely understand spectroscopy if this isn't taken into account.

 

[kuruman]

That is not true. There is a small probability the electron is in the nucleus. (Of order a few parts per million) But so what? Most of the time it just flies out again. Rarely it initiates a weak transition, as mentioned in post #2.

One cannot completely understand spectroscopy if this isn't taken into account.

A case in point is the Fermi contact interaction.