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Topic: Atoms Electrons and connectivity  (Read 3298 times)

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Offline Mr-E

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Atoms Electrons and connectivity
« on: August 22, 2013, 12:32:22 AM »
Hello everyone,
This will probably sound stupid to most of you but I am quite unsure as to how it works, even after reading the chapter twice.

The electrons around the nucleus don't fly away due to pull of the proton but what stops the electrons from being pulled so close to the proton that they are touching?

Cheers

Offline curiouscat

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Re: Atoms Electrons and connectivity
« Reply #1 on: August 22, 2013, 12:40:51 AM »
Hello everyone,
This will probably sound stupid to most of you but I am quite unsure as to how it works, even after reading the chapter twice.

The electrons around the nucleus don't fly away due to pull of the proton but what stops the electrons from being pulled so close to the proton that they are touching?

Cheers

What prevents the moon from crashing into the earth?

PS. This is the wrong ultimate answer but I'm just getting you thinking.

Offline Archer

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Re: Atoms Electrons and connectivity
« Reply #2 on: August 22, 2013, 02:09:43 AM »
This is the first question I got asked when I started A-level chemistry and the teacher was met with a sea of blank expressions so it's not a stupid question. Try reading around the topic, there may be a better explanation than your text book provides.
“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

Offline Mr-E

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Re: Atoms Electrons and connectivity
« Reply #3 on: August 22, 2013, 08:39:30 AM »
Thanks for the response curiouscat and Archer.
Very nice anecdote Archer and good advice, I will search around for better understanding of how electrons move etc.

That is quite interesting curiouscat, I can barely remember any information I have come across in regards to the moon and the earth and how it works but I will speak think out loud for a moment in regards to that.

I believe their is some pull inbetween the earth and moon, as from what I recall it even causes the ocean's tides. The moon moves along an orbit at what I assume can only be high speeds. As the moon doesn't go flying off in any direction there must be some force/attraction holding it on that path. So why doesn't it hit the earth? the speed... maybe the force pulling it towards the earth and the speed trying to keep it flying of equal each other?
I am not really sure.

This does get me thinking though, if the electrons can be anywhere within a certain range, then I can only imagine there is some type of back and forth going on... If I can remember right, I believe someone told me years ago that their path isn't as simple as the moon's path, they move all over the place, very random. Yeah I don't think I can work this out without reading more about it or without given some more useful tips.

Cheers

Offline Archer

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Re: Atoms Electrons and connectivity
« Reply #4 on: August 22, 2013, 09:33:22 AM »
Can I just say that I don't remember what the teacher said, I was only 16 at the time and more than 16 years have passed since that day. I vaguely remember the word quantum being used and still having no idea what he was talking about.

This page gives a good explanation

http://van.physics.illinois.edu/qa/listing.php?id=1226

“ I love him. He's hops. He's barley. He's protein. He's a meal. ”

Denis Leary.

Offline curiouscat

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Re: Atoms Electrons and connectivity
« Reply #5 on: August 22, 2013, 10:18:57 AM »

I believe their is some pull inbetween the earth and moon, as from what I recall it even causes the ocean's tides. The moon moves along an orbit at what I assume can only be high speeds. As the moon doesn't go flying off in any direction there must be some force/attraction holding it on that path. So why doesn't it hit the earth? the speed... maybe the force pulling it towards the earth and the speed trying to keep it flying of equal each other?

Yes, you are on the right track but I'd advise a High School Physics refresher: Read centrifugal / centripetal forces.

About electrons, it's a more complex explanation. @Archer gave you the tip there.

Offline Corribus

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Re: Atoms Electrons and connectivity
« Reply #6 on: August 22, 2013, 10:20:06 AM »
I think it's also important to point out that this kind of question is typical of students who haven't yet accepted that one has to abandon classical expectations when dealing with quantum systems.  To wit: unlike that of earwigs, eclairs, and elephants, the positions and momenta of moving electrons cannot be defined (simultaneously) with infinite precision.  We can only speak of probabilities with respect to where an electron is, where it's going, and how fast it's going there.  Were the electron to "fall" into the nucleus, we'd know exactly where it was, which would violate the laws of quantum mechanics. This is why in quantum systems there is usually a "zero point energy" - which is to say, most quantum systems can't have an energy of zero. They've ALWAYS got to be moving somewhere.

Here's another example that goes against our classical expectations and also illustrates the problem with illustrating orbitals as race-tracks that the electrons must ride along as they go around a nucleus. A p-orbital, which you'll learn about soon enough if you haven't already, has a "figure 8" shape, with the nucleus at the point where the two lobes meet. The electron, according to this simple conceptual model, must therefore be on one lobe or the other, and presumably it can go from one lobe TO the other since there is equal probability of finding the electron one one lobe or the other in any measurement.  To make a transit between one lobe to the other, though, the electron must go THROUGH the nucleus, but never actually be located AT the nucleus, because QM tells us there is a NODE at the nucleus where the electron can never, ever be.  How the hell does this happen?  It's like saying I can travel from New York west to San Francisco but I can never, ever be at a point halfway between them!

The answer (well, a partial, probably very unsatisfying answer) is that orbitals are only probability distributions and do not represent absolute, discrete position in time.  In fact we can't really say anything about where an electron is now, where it was one second ago, and where it will be one second from now: we can only say where it might have been one second ago, where it might be now, and where it might be a moment from now, and neither one of those has any direct causal relationship with any other.  In classical mechanics, if I know where a flying baseball is at this moment, its velocity, and any forces acting upon it, I can exactly specify where it will be in one second, ten seconds, and thirty seconds. I can also extrapolate and guess where it was one second ago.  Not so with electrons.  Even if I could specify where the electron is now, and know its velocity and forces acting upon it (which I can't), there's no way to predict where it will be in the near future or where it was in the recent past. The only thing I can say is where it is likely to be on average at any given point in time.

If you want to get philosophical about it, determinism goes right out the window in quantum mechanics, which is quite at odds with our macro-scale, classically deterministic experience with the world. This, by the way, was very unsettling to the scientists who originally discovered many of the principles of QM, Einstein included (who famously quipped 'God does not roll dice', to which Niels Bohr, a more ready supporter of the theory, retorted, 'Stop telling God what to do'). The point being that the predictions of QM are so at odds with our every day experience that we often get into trouble when we erringly apply classical logic to quantum mechanical systems.

Niels Bohr once also allegedly said (if we are to trust Heisenberg) that 'those who are not shocked when they first come across quantum theory cannot possibly have understood it'. Somewhat amusingly, Richard Feynman, one of the smartest quantum physicists who ever lived, conflictingly wrote, 'I think I can safely say that nobody understands quantum mechanics.' The experts can't even agree on whether their theory can even be understood! The point here being that with these things it's better I think to just learn the rules and accept them without digging too deeply at the 'why'.  What we do know is that the rules work, almost unerringly. I would leave the 'why' to the philosophers.
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

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