Why do electron spin

[Biosapien]

Hi everyone,

Could someone clarify the reason and what causes the electron to spin by itself and around the nucleus. Thank you.

[Faradave]

I'm afraid there is currently no accepted physical model of "intrinsic spin" though spinors offer an abstract mathematical model to work with.

You're welcome to read my short, accessible article proposing a physical model:
Spin½ 'Plane' & Simple

If you prefer animations: this is my first one dealing with spin.



Three more, extending the concept, are here:
Riding a Bi-Cycle (720° rotation)
Probable Cause (probability amplitude)
A Noether Round (new found symmetry)

[hyksos]

Hi everyone,

Could someone clarify the reason and what causes the electron to spin by itself and around the nucleus. Thank you.

I will address your question about why the electron revolves around the nucleus.

Classical physics was unable to explain the observed behaviour of electrons in atoms. Specifically, accelerating electrons emit electromagnetic radiation according to the Larmor formula. Electrons orbiting a nucleus should lose energy to radiation and eventually spiral into the nucleus. This is not observed. Atoms are stable on timescales much longer than predicted by the classical Larmor formula.

Also, it was noted that excited atoms emit radiation with discrete frequencies. Einstein used this fact to interpret discrete energy packets of light as, in fact, real particles. If these real particles are emitted from atoms in discrete energy packets, however, must the emitters, the electrons, also change energy in discrete energy packets? There is nothing in Newtonian mechanics that explains this.

The de Broglie hypothesis helped explain these phenomena by noting that the only allowed states for an electron orbiting an atom are those that allow for standing waves associated with each electron.

The above material was copy-pasted from here :

https://en.wikipedia.org/wiki/Theoretical_and_experimental_justification_for_the_Schr%C3%B6dinger_equation
That was an attribution, and I don't suggest reading it.

If you want to learn more, this article is okay : https://en.wikipedia.org/wiki/Atomic_orbital

or https://en.wikipedia.org/wiki/Hydrogen-like_atom

[Faradave]

The de Broglie hypothesis helped explain these phenomena by noting that the only allowed states for an electron orbiting an atom are those that allow for standing waves associated with each electron.

Well stated. I was tempted to address orbitals the same way, as it is exactly what I've found. Biosapien should accept the above as the proper physics answer.

The explanation however, never quite resonated with me personally. As you noted, if an electron accelerates anywhere besides in an atomic orbital, it radiates energy electromagnetically. This can be by linear acceleration or by changing path direction, as in a cyclotron. What makes the atomic orbital an exception is that they correspond to standing waves. To be sure, I concede the correspondence and consider it a major discovery. But...

Consider a tuned piano string. If struck, it emits a sound characteristic of its fundamental resonance and perhaps some harmonic overtones (higher resonances). So, instead of containing the energy imparted by the strike, the spring most preferably emits energy at standing wave frequencies.

The same occurs if an adjustable mechanical oscillator is attached to the spring. As it sweeps through a range of frequencies, most will strain the spring, heating it to then be slowly dissipated. But at standing wave frequencies, a much greater portion of the energy will be emitted as sound.

So, if orbitals in any way represent motion (necessarily acceleration) of an electron, they should enhance energy loss, leading to even quicker collapse into the nucleus.

Conclusion: It is more consistent to think of the standing wave regions about a nucleus as being those which support superposition as an alternative to any sort of classical motion. Superposition should be considered a state of instantly and probabilistically occupying such a region. It is a state of being rather than one of moving. No acceleration, thus stability with no emission.

[Biosapien]

Hi guys, thank you for such a detailed explanation, but as a biologist it will take some time for me to visualize and understand the concepts which you have explained. I am not interested in understanding the "model of why electron spin" rather I simply want to understand why the electron spin based on following aspects. Since electron has a mass it need some kind of external force for its spin or revolving around the nucleus and which driving force causes the electron to spin, whether is it the force from the nucleus of the atom or some other external force. If its due to force from nucleus then why the electron has not been pulled into the nucleus because opposite charge attracts each other and the mass of atomic nucleus is 1000 time larger than electron. How electron escape from a such a huge force of attraction. When the Oxygen steals the electron from Hydrogen or any other atom which force of the Oxygen atom is responsible for reduction reaction.

[Faradave]

I simply want to understand why the electron spin...

Simple questions don't always have simple answers. Your question arises naturally from picturing (i.e. modeling) an electron as a classical object, such as a very tiny stone. That is not how particle theory models a fundamental particle. You might as well ask why does an electron have mass, gravity or electric charge. Intrinsic spin is at least as fundamental as any of those.

"...the recent advent of quantum mechanics was radically altering the conception of particles, as a single particle could seemingly span a field as would a wave, a paradox still eluding satisfactory explanation."

As a biologist, it will be easiest to accept that fundamental objects, such as electrons are not a classical objects and thus, exhibit non-classical behaviors. Large classical objects also have such behaviors but they are lost in their average. Similarly, a jar of hot gas can be standing still on average, even though its constituent particles are vigorously moving.

[Biosapien]

Hi Faradave, Thank you for explaining the facts in a much more simplified manner.