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Electron field

  1. Jul 1, 2011 #1
    It is stated that electrons orbit the nuclei of atoms not as particles. By the Heisenberg Uncertainty Principle (whatever that is) one cannot pinpoint their actual location and one cannot track the motion of an electron as it orbits the nucleus.

    What is that all about? Please use 10th grade English or College freshman English to explain.
     
  2. jcsd
  3. Jul 1, 2011 #2

    mathman

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    The simplest answer is that "orbits" are not an accurate description of electrons in atoms. The only accurate description is in terms of quantum states, without trying to specify location.
     
  4. Jul 1, 2011 #3
    Electrons imagined as oribiting point particles around a central nucleus is NOT an accurate atomic model: such a model works for the large scale, like planets, but NOT for subatomic particles. In fact if such a model is used, the electrons would immediatly collapse into the nucleus. Quantum theory, of which Heisenberg uncertainty is a component, is required to explain electrons more as a cloud enveloping a nucleus, a spread out phenomena, rather than a point like particle.

    More here:
    http://en.wikipedia.org/wiki/Atomic_orbital#Introduction


    And here is some info on Heisenberg uncertainty:
    http://en.wikipedia.org/wiki/Heisenberg_uncertainty_principle
     
  5. Jul 1, 2011 #4
    In the atomic realm (very tiny things) objects usually act as though they are waves and not little solid balls. This means an electron more closely resembles ripples in a bucket of water. They are all over the area of the bucket and you can't point to any one place and say that's where the thing actually is.
     
  6. Jul 1, 2011 #5

    alxm

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    Last edited by a moderator: Apr 26, 2017
  7. Jul 1, 2011 #6
    So, it is stated that an electron is not a particle but a standing wave about a nucleus and the wavelength times a whole number is the circumference of the orbit.

    So where is the probability factor? Since there is no particle there is no way to know where such a non existent particle is, just where the whole energy wave is as a whole.

    Now is the energy wave up and down from the orbital? (Up meaning away from the nucleus and down meaning towards the nucleus)?

    Now, interestingly enough, when we describe in probability and statistics a probability density function, such as the normal curve, there is NO probability of finding a particular point on the x-axis but the probability of being within x = x' [itex]\pm[/itex] [itex]\epsilon[/itex] is the area of the probability function between x = x' - [itex]\epsilon[/itex] and x = x' + [itex]\epsilon[/itex]. I see the parallel but don't get the connection.
     
  8. Jul 1, 2011 #7


    Did you read here:

    http://en.wikipedia.org/wiki/Atomic_orbital#The_shapes_of_orbitals

    That's as good a simple description as you'll likely find.

    ok here is another not too complicated:

    "The Schrödinger equation details the behaviour of ψ but says nothing of its nature. Schrödinger tried to interpret it as a charge density in his fourth paper, but he was unsuccessful.[12] In 1926, just a few days after Schrödinger's fourth and final paper was published, Max Born successfully interpreted ψ as a quantity related to the probability amplitude, which is equal to the squared magnitude of ψ.[13] Schrödinger, though, always opposed a statistical or probabilistic approach, with its associated discontinuities—much like Einstein, who believed that quantum mechanics was a statistical approximation to an underlying deterministic theory— and never reconciled with the Copenhagen interpretation.[14]"

    from Wikipedia, "Schrodinger wave equation"
     
  9. Jul 1, 2011 #8
    They orbit the nuclei when they are in hyperexcited states. Then they go round and round the nucleus like little planets, except the force keeping them there is electromagnetic, not gravitational.

    By 'hyperexcited' I mean they have a lot of energy compared to normal, and that lets them revolve around the nucleus very far away.

    But when they are very close, their wave-length (properties) are around the same as the scale of the the close-up region. Now the electrons are behaving more and more like they are waves, and there is much uncertainty about just where a wave's 'position' is.
     
  10. Jul 2, 2011 #9
    This is what I am getting to... everything seems to "beg the question." The electron is BOTH wave and particle simultaneously. Now, as a wave, it is a standing wave in circular (elliptical) format that goes around the nucleus. As a wave, it has a wave length and the wave length is a natural number divided into the circumference of the orbit (so to speak). As a particle, it just orbits the nucleus in an ellipse.

    Einstein believed everything was deterministic. The only "probability" was that we, as yet, did not have the tools or the mathematical equations to pinpoint the position/momentum of the electron as a particle. As a wave, there is no specific point where it is because its a wave.


    Please comment on what I italicized above.
     
  11. Jul 2, 2011 #10
    You've accidentally italicized all of it, but I think you're on the right track. You cannot pinpoint the position/momentum simultaneously because they are aspects of the same thing, and a tool good for measuring momentum is bad for measuring position, and particle-ness measuring devices are commensurately bad for measuring wavs. So when something unclassical like an electron comes along which seems to have wave and particle properties, then it's pretty hopeless.

    Everytime a new paper comes out claiming to nail X, someone comes along and says they really nailed Y, and least as far as I can determine from the prose in the popular press.
     
  12. Jul 2, 2011 #11
    That assumes that the measuring of the position or the velocity (i.e., momentum) of an electron as it is orbiting impacts on the measurement of the other "parameter." In a theoretical sense, even though we cannot measure both at the same time because of the restrictions of the measuring devices, these two quantities (position and momentum) DO exist and "God" knows what they are.

    However, if an electron existed as a standing wave with an integral number of wavelengths to circumnavigate its orbit, where it is as a particle at any point in time is not possible to discern because all points on this orbit are possibilities at the same time and each instant in time thereafter, no matter how close or how far from the original point has an equal likelihood of being where this electron as a mass point would be.

    Note the use of "likelihood" as opposed to probability. In statistics a quintessential probability density function is the normal distribution curve with area of 1 under the curve with a continuous variable (call it "x") on the abscissa. The ordinate component is NOT the probability of finding "x" but the likelihood. The probability is the area between x1 and x2 divided by 1.
     
  13. Jul 2, 2011 #12
    I believe there is a school of thought that holds an agnostic view that the electron does not have any actual position until it is measured. God can't know what does not exist. 'measured', here, meaning any interaction that requires its position. There is a horrible philosophical debate over whether a conscious entity is entailed by 'measure', and it's way beyond me.

    But you wanted grade 10 or 1st year prose anyway.
     
  14. Jul 2, 2011 #13
    Hey, let's not get into that... "Does a tree falling in the woods with no one around make a noise?" It may or may not make a sound but it sure thinks to itself, "Aw, sh--!"

    What I am stating is that the reason for the unpredictability of the position of an electron in the "electron cloud" about a nucleus is that there is no one point at which it exists. If the electron is a wave then any point of condensation is anywhere on the wave at the same time Make sense? This has nothing to do with the manner of measurement or the effect of measurement on the position/velocity of the electron.

    This is 10th grade-freshman college level English which actually is far superior to technical jargon.

    BVy the way, I am just taking the info given to me above in the earlier posts about the "standing wave," etc. and applying common sense to it.
     
  15. Jul 3, 2011 #14
    If I say: 'if the electron is a wave...', then I'm presupposing my manner of measurement, and I'm unable to say anything about a point of condensation, or an 'anywhere' on the wave. I figure all I can do with wave (deliberately omitting a determiner that would imply a count-noun) is talk about its momentum.
     
  16. Jul 3, 2011 #15
    I am lost in the details. Don't bother going over it again.

    Should I accept the Heisenberg Uncertainty Principle? Is it true? Can certain chemical reactions (Stanley Miller's 1950s experiments with abiotic production of prior only organic compounds made by living organisms later finally redone 60 years later after many failed attempts to reproduce the results) be an extrapolation of this?
     
  17. Jul 3, 2011 #16
    Personally I take it on experience that every time they try to nail down both attributes of some quantum entity, someone says something like: Well they thought they were measuring X, but really they were measuring Y. Or a proxy-X, or an ensemble X, or type-X, not a token-X. That's how my reading of pop science of these things seems to go. So I'm pretty confident about Heisenberg.

    It's not whether it's true or not, but whether it's falsifiable (yes), and has it been falsified. Not as far as I know. So after hundreds of tests, the confidence-level is absurdly high. But 'true'? Pretty true.
     
  18. Jul 4, 2011 #17
    Now, to make things clear, one corollary of the HUP is that of predicting the location of an orbiting electron - which Heisenberg says you cannot do with absolute certainty. It also means that from one instant to the next, no matter how close these "instances" are, a particular electron can be anywhere else in the electron cloud around the nucleus.

    I think my interpretation as just stated is correct (forget about momentum for now.) Hence, my reliance upon the "wave" theory of an electron as a wave has NO point on it which is an electron.

    PS _ I really enjopy thios bantering back and foprth. Not many people I know persoanlly can even discuss this on any level so you are a welcome relief.
     
  19. Jul 6, 2011 #18
    I'm actually a physics idiot. My real field is linguistics. I'm sorry you're not getting a more precise discussion, because you seem to have a better handle on this topic than your opening statement implied.

    You may also want to explore the deBroglie/Bohm model of the electron that holds the electron is a real point-particle with a real (but theoretically undeterminable ) position at all times, and its wave-function is more like an actual field, than just a mathematical construct for determining the mere probability of its position at any point. This old idea seems to be having a renaissance, with some smart arguments on both sides, but rather technical and over my head. Those discussions are actually pretty lively at times around PF, and you just have to look around for them. I have no bias one way or the other.
     
  20. Jul 6, 2011 #19
    Not quite a physics idiot that you state - just a non-physicist who has an interest in these matters. If you think about it, if the electron were a point particle, then the probability of finding it at any arbitrary point on the orbiting spheroid or ellipsoid would be zero. As I have mentioned above using the normal distribution curve as an example, with the x-axis being the continuous variable, then the y-axis is the likelihood, not the probability, of such a value.

    I am not a physicist either, just a medical doctor with an interest in these matters.

    That's why the concept of a standing wave makes sense, because a wave has zero probability of a particular point but a total probability of one (1) and is continuous. It is everywhere simultaneously equally likely, or, at least a smooth relationship between the different points on the spheroid/ellipsoid.

    There is a neat problem from topology that states there are at least two points on the globe in which the pair barometric pressure and atmospheric temperature are the same - due to continuity.
     
  21. Jul 7, 2011 #20
    I use stats terms loosely, and oddly the term 'likelihood' is absent from the major Wiki entries (though Google returns pages missing it anyway) on wave function.

    I'm not sure it's safe to compare two scalar correlations with point and momentum correlations.
     
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