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Offline PicturesOfLilly

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Miscellaneous Questions on electronic orbitals
« on: September 18, 2020, 11:11:49 AM »
So I'v a few questions based on the following video which I'd like to answered in the context of the following video. Answer only the ones you wish, and maybe just take a brief look at the video first so all this doesn't seem so random.

https://www.youtube.com/watch?v=P2IsIkSn5bk&ab_channel=Barthek88

1. When it mentions electron spin (at 1:23), I presume that means spinning of the electron on its own axis? So assuming I'm right with that, does "not perpendicular to trajectory" mean the same as saying parallel to trajectory?

2. Also, do the electrons go right through the nucleus? Shouldn't they be going faster when they're closer to the nucleus?

3. In the case of lithium, it seems to be that it's the same electron each time that is the one that goes into the outer shell. Would I be right in saying that that is the electron that is changing energy levels (& not the other two)? and that it changes E levels randomly; with there being a higher probability of it being in the higher E level?

4. Taking boron as an example; if you were to measure its electron cloud over a short period of time, would it appear darker on one side? (due to the lobe sticking out of it)? And would I be right in saying that you'd have to keep taking measurements of the electron position within boron over a longer period of time that it would the darkness of the electron cloud eventually average out?

5. The other thing is that this video shows the electron in a way that can clearly be understood. I thought quatum mechanics proved that electrons are "everywhere at once". And if that's completely true, then a clear visual representation of how electrons move will never be possible, and that therefore everything in the above fvideo is incorrect.

6. At 6:39 in this other video (don't need to watch it) we see it being explained that the 5th electron in the case of Boron, would be going into the double lobed shape represented in pink.

https://www.youtube.com/watch?v=Ewf7RlVNBSA&ab_channel=CrashChemistryAcademy

But yet in the main video I've posted here, we see from 3:10 that the 5th electron of Boron being shown in such a way that there is only a lobe on one side! So that cannot be true????

7. Just to make a reference to Louis de Broglie for a sec; he reasoned that an electron was between energy levels that it would be out of phase with itself, and would interfere with itself. I don't see why. Think of it this way:

Take the same concept with water waves in two different channels that meet up; okay, they interfere with each other some how if they're not perfectly in phase. But now lets take that same water wave in a narrow channel that's in the form of a circle! If you were to follow a wave all the way around the channel, the chances are that by the time one lap has been completed, that any given crest or trough will not be at the exact same part (on the wall) that it would have been previously. But the water doesn't know any different. So why would it make any difference with the electron? So I don't see how the electron could "interfere with itself"! ???

Thank you for reading
« Last Edit: September 18, 2020, 11:28:28 AM by PicturesOfLilly »

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Re: Miscellaneous Questions on electronic orbitals
« Reply #1 on: September 18, 2020, 01:11:37 PM »
1. When it mentions electron spin (at 1:23), I presume that means spinning of the electron on its own axis?

No, it means https://en.wikipedia.org/wiki/Spin_(physics)

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2. Also, do the electrons go right through the nucleus?

No, they don't behave like point objects and they don't "move" in a classic sense.

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3. In the case of lithium, it seems to be that it's the same electron each time that is the one that goes into the outer shell.

No way to distinguish between electrons, so you can't say which one it is.

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5. The other thing is that this video shows the electron in a way that can clearly be understood. I thought quatum mechanics proved that electrons are "everywhere at once". And if that's completely true, then a clear visual representation of how electrons move will never be possible, and that therefore everything in the above fvideo is incorrect.

Bulls eye ;)
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Offline PicturesOfLilly

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Re: Miscellaneous Questions on electronic orbitals
« Reply #2 on: September 20, 2020, 03:19:32 PM »
Quote
5. The other thing is that this video shows the electron in a way that can clearly be understood. I thought quatum mechanics proved that electrons are "everywhere at once". And if that's completely true, then a clear visual representation of how electrons move will never be possible, and that therefore everything in the above fvideo is incorrect.

Bulls eye ;)

So you're saying that whoever made this video just made the whole thing up? Wasn't de Broglie's theory based on the assumption that electrons behaved as point objects?

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Re: Miscellaneous Questions on electronic orbitals
« Reply #3 on: September 20, 2020, 04:34:50 PM »
So you're saying that whoever made this video just made the whole thing up?

It is not like the video is completely made up, but it reproduces some misconceptions and mixes truths, half truths and made up things.

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Wasn't de Broglie's theory based on the assumption that electrons behaved as point objects?

It was. And despite being wrong in this assumption it did have its successes. Doesn't mean it was correct. It was only a low level approximation that got quickly replaced by an approach that is much better in terms of its validity, but much more difficult to intuitively understand.
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Offline Enthalpy

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Re: Miscellaneous Questions on electronic orbitals
« Reply #4 on: September 21, 2020, 03:12:27 PM »
Don't spend time on this video, it contains many misconceptions that will disturb you when learning further.

As you noted, electrons are simultaneously at all the positions covered by the wave function. And at an orbital, which is a stationary wave-function (but not all wave functions are stationary), there is nearly no evolution over time at all. It's nearly the idea of "immobile", which explains why the electron doesn't radiate light when it's a stationary wave function, except that p, d... wave functions have an orbital momentum and a magnetic momentum. Any video, any explanation that shows a point moving on an ellipse is contrary to quantum mechanics.

As spherical orbitals (1s, 2s... not 2p, 3p, 3d...), electrons have a strong probability density right at the nucleus. I don't know of an interaction that would limit the proximity of an electron with a proton or neutron, or with a quark blah blah blah. You may want to consider the nucleus as a point or as an object with some extension, much smaller than the electron's orbital.

The "speed" of the electron is a subtle idea. Because the electron is simultaneously everywhere, it's speed, momentum, kinetic energy is often given as a single global value. Then, the electron can have a mean kinetic energy, no mean momentum nor speed as it's centred on the nucleus, but nevertheless an orbital momentum. This is central to quantum mechanics, whose first task was to explain why the electron doesn't radiate photons and fall on the nucleus, and it's answer was to make the idea of movement more subtle.

Sometimes we need the kinetic energy or momentum of an electron within a limited volume of its wave function. This happens when an energetic photon ionizes an atom for instance, and the total energy and momentum are conserved. It's also necessary to compute the relativistic correction to the mass of the electron and its effect on the orbital's energy: only a local correction of the mass gives the experimentally observed values, not one global correction (my professor got it wrong here, many books too). So a local kinetic energy is useful and meaningful, and indeed, it's bigger near to the nucleus, up to really big values.

==========

My first suggestion would be to peep at the cute illustrations of orbitals there
https://winter.group.shef.ac.uk/orbitron/

==========

My second recommendation is to choose very carefully your source of knowledge, even more so for quantum mechanics. QM is a century old, its interpretation evolved awfully much, but most books are brutally outdated and still propagate misconceptions and abandoned models dating back to Bohr or others. Things like "duality" and other philosophical concepts bring zero dot nothing to the understanding. Avoid also general public science reviews: the authors generally don't understand the topic and revert to images that obfuscate QM.

Even reputable authors carry bizarre and unjustified explanations. BUT the maths tend to be correct in every book, probably because the authors didn't dare to alter a comma on something they don't grasp. So my third suggestion, if you know enough maths, is to learn QM by its maths. Reject all images and explanations brought by the authors (especially when you see points or any evolution over time). Take the mathematical expression, and ask yourself "what does it imply for the electron, and what is not implied".

For instance, do you see a time dependence in the orbital? No? Then, don't add any sort of trajectory for the electron.
Do you see any axis and rotation in the expressions for the spin on x, y, z of the electron? No? Then there is none.
Does something in the wave function tell "I am only a way to compute a probability of presence"? No? Thrash.
Be as fundamentalist as an ayatollah with that. The maths tends to come unaltered from the few people who grasp QM. The blah blah around uses to be wrong. Even from the best authors. As an illustration, every second author or professor claims that the BCS model for superconductivity includes a Bose-Einstein condensate, which proves that every second author of QM book misunderstood both the BCS model and the Bose-Einstein condensates.

One possible exception is the collapse of the wave function in an interaction. Much of it is flawed, but some of it may survive. This seems to be an open question in the interpretation of QM - but I'm not on the edge.

And: read some recent information from QM. For instance, the nice images of pentacene by atomic force microscope (AFM) corrects misconceptions that the dual slit experiment allows. Recent experiments (especially in Munich) made some cleaning among the many interpretations of QM and made QM itself more concrete in many ways.

Feyman wrote excellent books about QM, if the maths is accessible to you. He took care not to introduce mental representations not implied by experiments and the maths modelling. But he doesn't explicitly dismiss the wrong mental representations introduced by other authors, alas.

Offline Corribus

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Re: Miscellaneous Questions on electronic orbitals
« Reply #5 on: September 22, 2020, 10:01:53 AM »
All very well and good, Enthalpy. The problem is that most chemistry students aren't up to understanding differential equations. Yet QM is so central to modern chemistry that it must be taught in some rudimentary form. What's the resolution?
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline Enthalpy

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Re: Miscellaneous Questions on electronic orbitals
« Reply #6 on: September 23, 2020, 03:50:13 PM »
[...] most chemistry students aren't up to understanding differential equations. Yet QM [...] must be taught in some rudimentary form [...]

Oops, I hadn't expected that one. So true! For electrical engineering, QM can wait a few years since only semiconductors need it. For chemistry it can't.

Then, explaining and telling stories without maths, yes. I have absolutely nothing about such an approach, since I did much so with electronics as a teen. Qualitative understanding can be more detailed and creative.

If I had to give such explanations, I'd try to rely heavily on recent experiments. Some give nice pictures (atomic force microscope) that stabilize the understanding. Others filter out good interpretations of wave functions from dead ones.

Building on solid knowledge for waves (acoustics, radio, optics) helps a lot, but maybe undergraduates don't have learned this.

Offline PicturesOfLilly

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Re: Miscellaneous Questions on electronic orbitals
« Reply #7 on: September 25, 2020, 09:16:18 AM »
Thank, but I think that big long post of yours, either confused me more, or went over my head.

Don't spend time on this video, it contains many misconceptions that will disturb you when learning further.

But the second video I posted make more sense I think. Could you do me a favour, and answer question 6 by any chance? It compare a contradiction in the two videos I posted. At least that way I might be able to understand properly, the areas within which electrons (of certain E levels) are found, even if I don't understand how they move.

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Re: Miscellaneous Questions on electronic orbitals
« Reply #8 on: September 25, 2020, 09:55:22 AM »
Could you do me a favour, and answer question 6 by any chance? It compare a contradiction in the two videos I posted.

In this particular moment first video tells bulls&$# about the shape of the orbitals. Best advice we can give you is: forget you ever saw that.
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Offline PicturesOfLilly

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Re: Miscellaneous Questions on electronic orbitals
« Reply #9 on: September 25, 2020, 04:27:48 PM »
Could you do me a favour, and answer question 6 by any chance? It compare a contradiction in the two videos I posted.

Best advice we can give you is: forget you ever saw that.
And then what? Keep asking you questions as you get off on my misery?

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Re: Miscellaneous Questions on electronic orbitals
« Reply #10 on: September 25, 2020, 07:40:12 PM »
PicturesofLilly, why don't you reframe your question without making reference to the videos. Videos on the internet are a mixed bag and it's hard for students to know what is reliable and what isn't. What are you having trouble understanding?
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Re: Miscellaneous Questions on electronic orbitals
« Reply #11 on: September 26, 2020, 03:27:17 AM »
Best advice we can give you is: forget you ever saw that.
And then what? Keep asking you questions as you get off on my misery?

And then learn from the reliable sources. Yes, it is sometimes hard to say which source is reliable, but we already told you the one you are asking questions about is a trash, so why do you stick to it?

People say plenty of things that are wrong and stupid. If I say '2+2=5' will you start asking around why I wrote that, or if perhaps I am right, or will you just shrug, think "what an idiot" and move along?
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Offline Meter

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Re: Miscellaneous Questions on electronic orbitals
« Reply #12 on: September 26, 2020, 08:27:43 PM »
Chemistry is full of misnomers which were originally coined by scientists who either had incomplete or simply incorrect understandings of the concepts they were studying. For example: oxidation isn't exclusive to reactions involving oxygen, but because the original investigations into what we now call oxidations involved oxygen, the term has been coined as such. This is an example of how misnomers arise from incomplete understanding.

The property of electron "spin" was coined as such because electrons appeared to exhibit a magnetic field (even at rest), and it was thus theorized that electrons must have some sort of rotational movement which accounts for this field. This is wrong, however, as electrons are point-like and don't spin around an axis (like a globe or whatever). Rather they have intrinsic angular momentum, which is equally confusing, but the fact that it is intrinsic just means "deal with it, it exists". I like to think of spin as a property which gives rise to a magnetic field much like how mass is a property which gives rise to a gravitational field. I can accept the latter, so why not accept the former?


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Re: Miscellaneous Questions on electronic orbitals
« Reply #13 on: September 27, 2020, 10:22:08 AM »
This is wrong, however, as electrons are point-like and don't spin around an axis (like a globe or whatever). Rather they have intrinsic angular momentum, which is equally confusing, but the fact that it is intrinsic just means "deal with it, it exists".
There are certainly some things that must just be accepted as axiomatic by students of elementary chemistry and physics - and indeed, even from a seasoned chemist's view, some things need not be explained further - but it is unfair to say that science in general treats unexplained phenomena this way. There are reasonable and tested theories about why electron spin exists, despite their "pointlike" nature. I believe the current thinking involves virtual photon formation in the electric field generated by an electron in motion, or some such. That's definitely a topic more in the realm of theoretical physics than chemistry, but it's important not to give students the wrong idea here. Most great discoveries, quantum mechanics chief among them, came about exactly because people made a deliberate choice to not just "deal with it".
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Offline Meter

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Re: Miscellaneous Questions on electronic orbitals
« Reply #14 on: September 27, 2020, 10:46:25 AM »
This is wrong, however, as electrons are point-like and don't spin around an axis (like a globe or whatever). Rather they have intrinsic angular momentum, which is equally confusing, but the fact that it is intrinsic just means "deal with it, it exists".
There are certainly some things that must just be accepted as axiomatic by students of elementary chemistry and physics - and indeed, even from a seasoned chemist's view, some things need not be explained further - but it is unfair to say that science in general treats unexplained phenomena this way. There are reasonable and tested theories about why electron spin exists, despite their "pointlike" nature. I believe the current thinking involves virtual photon formation in the electric field generated by an electron in motion, or some such. That's definitely a topic more in the realm of theoretical physics than chemistry, but it's important not to give students the wrong idea here. Most great discoveries, quantum mechanics chief among them, came about exactly because people made a deliberate choice to not just "deal with it".
Physicists are notoriously unsatisfied with the idea of "that's just how things are", and thank lord for that! But as chemists (and chemistry students) there comes a point where we shouldn't look deeper and simply accept that certain phenomena are emergent properties of a deeper level of physics. Or maybe we should - but at that point you become more of a physicist than a chemist in my opinion.

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