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Topic: Electron has volume or not ??  (Read 1872 times)

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Offline AdiDex

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Electron has volume or not ??
« on: November 27, 2016, 03:50:51 AM »
Sometimes we say that electron has volume , as in orbital we can define it's volume (atleast for some fraction , as orbital itself has no limit ,it is spread all over the space expect nodes ) 

On other hand In general Chemistry books often spin quantum no. is referred as electron spinning on its axis . But this is absurd , because this magnetic angular momentum is an intrinsic property of the electron . Also that an Electron is an elementary particle , it is 1-D (No volume) . So it's not possible for an electron to spin on it's own  axis .

So what's the matter , do electron has volume or not .?

What I think that it's a particle , but we can't describe it's position what we can do is Probabilistic Approach , we can only describe some region where we can find it more likely or less likely . We defined It's volume , otherwise electron themselves has no volume . Even it is more weird that electron is everywhere in the orbital  ;D

I have knowledge of quantum mechanics (but only little) . Can somebody explain it ??

Offline Borek

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Re: Electron has volume or not ??
« Reply #1 on: November 27, 2016, 04:32:17 AM »
Sometimes we say that electron has volume , as in orbital we can define it's volume

Orbital is not an electron, electron is not an orbital.

Don't bother with the spin being an effect of rotation, this is a nonsensical explanation. Reasonable analogy in some aspects, but producing more confusion than it is worth IMHO.

So what's the matter , do electron has volume or not .?

It is a point particle with no volume.

Volume of particles is a property that is part not of the quantum mechanics (which just assumes point like particles, even for those with a known volume), but a theory of elementary particles (so called Standard Model).
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Offline Enthalpy

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Re: Electron has volume or not ??
« Reply #2 on: November 30, 2016, 03:14:16 PM »
I like to confound the electron and its wave, and say short "the electron's volume".

In favour of this: the wavefunction is much more than a means to compute a probability to find the electron in a region. An electron interacts simultaneously from all the positions covered by the wavefunction. And for instance in an atomic force microscope, the interaction lets "feel" the orbital's shape without destroying it.

In some cases, an occurred interaction has reduced the size of the electron (or of its wavefunction if you prefer). This happens in a double slit experiment, where the detector tells where the electron has been observed, and the fringe wavefunction predicts the probability of detection over the pattern. But this one case should not be overinterpreted nor overgeneralized.

If for instance a quantum well or a superlattice absorbs a photon, this happens over the full size of the component, over which the absorbing electron is delocalized before and after the interaction. This is the only possibility to explain the energy gap, the sensitivity to polarization, the detector's directivity. Absorption by an electron local to an atom, before or after the event, would not explain that. By a point electron, neither.

What we do need from a particle is that, when the electron (electron's function if you wish) changes its size and shape at an interaction, some attributes are conserved and don't split, for instance the charge and the spin. This is a basic difference with a classical wave. But beyond that, we need really little from a particle.

So an interaction would mean something like "since the other object acts in that volume and when the interaction has happened, from that time on, the particle starts with such a wavefunction (if it still exists)". If the electron has passed the slits, which we know because we detected it downstream, then we know that its wavefunction had the shape of the slits when it passed through, and we can deduce the fringe pattern of its wavefunction downwards. And if it made a current in pixel 573, we know that its wavefunction adapted to that pixel's size and shape.

"Point particle" is less than simple. First, we can't observe it, as it would demand infinite energy. What is observed is that, within all the particle energies that humans can produce, the electron has the ability to keep some attributes (charge etc) unsplit within the tiny interaction volume. So "point" means "as small as we can do up to now".


A proper answer would be longer and more complicated than that I guess, and would neither be "point" nor "spread". It would probably contain "ability to reshape" and "unsplit properties".

With that in mind, I like to write "the particle is the wave" because it avoids some misinterpretations (especially the common one of waves serving only to compute probabilities of interactions that would be points - that's plain wrong). While my wording isn't very common, I have good companions here, for instance Schrieffer (from the BCS superconductor theory).

But with this simplified wording, one must keep in mind that such waves aren't classical, in that particles don't split. And also, that several particles still are one single wave, unless their history makes them independent.

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