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Iceking20
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- Do electrons accelerate when they absorb or emit energy?
Do electrons have motion or they just accelerate when they get enough energy?
For bound electrons (the ones that move from one energy state to another in an atom) it makes no sense to talk about their position, speed, or acceleration. The classical idea that the electron is some small object moving around the nucleus just doesn’t work in the quantum mechanical description.Iceking20 said:Summary: Do electrons accelerate when they absorb or emit energy?
Do electrons have motion or they just accelerate when they get enough energy?
Yes the electrons have continuous motion if that's what you mean. Thus we can have position vector, velocity vector and acceleration vector assigned to an electron.Iceking20 said:Summary: Do electrons accelerate when they absorb or emit energy?
Do electrons have motion or they just accelerate when they get enough energy?
Delta2 said:the electrons have continuous motion if that's what you mean. Thus we can have position vector, velocity vector and acceleration vector assigned to an electron.
Delta2 said:according to the laws of quantum physics , which currently is our best theory for the behavior of microscopic particles like electron, we cannot determine their position vector and their velocity vector or their acceleration vector
I don't understand. In quantum physics the electron is a point particle (true or false?). So it arises the question how does it move? Does it move like a point particle along a curved path (mith multiple zig zags e.t.c) which we just can't determine (because we don't have yet the appropriate theory) and so we can speak only with probabilities about its location and movement? Or what does it hold about the movement of electron in the regime of quantum physics?PeterDonis said:This is only true if we are treating the electron classically. In some contexts (for example, electrons in a cathode ray tube) this can be a useful approximation, but it is only an approximation.
Delta2 said:In quantum physics the electron is a point particle (true or false?).
Delta2 said:how does it move?
I might be interpreting your answer incorrectly but there seems to be a contradiction in what you wrote:Nugatory said:For bound electrons (the ones that move from one energy state to another in an atom) it makes no sense to talk about their position, speed, or acceleration. The classical idea that the electron is some small object moving around the nucleus just doesn’t work in the quantum mechanical description.
That word could have been “change” or “transition”. There’s no more physical movement involved than when someone “moves” from one political party to another, or when public sentiment “shifts” on an issue, or a video game player “moves” to the next level.Dadface said:You refer to bound electrons as moving "from one energy state to another"
Due to the Kochen-Specker and other no-go theorems we know that if an electron really has a definitive position then it's either communicating with its past self in some manner or it can influence other particles faster than light.Delta2 said:I don't understand. In quantum physics the electron is a point particle (true or false?). So it arises the question how does it move? Does it move like a point particle along a curved path (mith multiple zig zags e.t.c) which we just can't determine (because we don't have yet the appropriate theory) and so we can speak only with probabilities about its location and movement? Or what does it hold about the movement of electron in the regime of quantum physics?
As others told you, this question does not make much sense within standard QM. But it makes perfect sense within Bohmian formulation of QM, in which case the answer is - fundamental particles have motion and accelerate. There are, however, reasons to think that electron may not be a fundamental particle (see the paper linked in my signature), in which case motion and acceleration should not be associated with electrons but with some more fundamental particles.Iceking20 said:Summary: Do electrons accelerate when they absorb or emit energy?
Do electrons have motion or they just accelerate when they get enough energy?
Nugatory said:That word could have been “change” or “transition”. There’s no more physical movement involved than when someone “moves” from one political party to another, or when public sentiment “shifts” on an issue, or a video game player “moves” to the next level.
DarMM said:QM itself is completely silent on the issue and does not refer to electron trajectories at all.
Demystifier said:As others told you, this question does not make much sense within standard QM. But it makes perfect sense within Bohmian formulation of QM, in which case the answer is - fundamental particles have motion and accelerate. There are, however, reasons to think that electron may not be a fundamental particle (see the paper linked in my signature), in which case motion and acceleration should not be associated with electrons but with some more fundamental particles.
Dadface said:Suppose a hydrogen atom in the ground state became ionised. Are you saying that there is nothing equivalent to change of position and therefore movement during the event?
Dadface said:does QM and any interpretations of it forbid movement?
Dadface said:In light of this what is meant by statements of the type:
The most probable separation between the electron and proton in the ground state hydrogen atom is equal to the Bohr radius.
PeterDonis said:There is no definite position, velocity, or trajectory for the electron.
The math of QM says what I said above. Interpretations like Bohmian mechanics talk about "positions", but these positions are unobservable.
That the radial part of the ground state wave function for the electron in the hydrogen atom, in the position representation, has a peak at that radius.
Dadface said:I was enquiring about "change of position". Is there anything in QM that disallows changes of position, albeit that these changes are not definite.
Dadface said:I think the observations we do have, for example from excitation and de excitation events, provide some evidence that the separation between the proton and electron does change.
Dadface said:Are the electron and proton best described in terms of mathematics and things such as peaks in wave functions.
Dadface said:I'm wondering if such descriptions can accommodate measured properties such as charge.
PeterDonis said:If there is no definite position, there is no definite change of position.
No, they provide evidence that the energy of the electron changes. None of these measurements involve measurements of position, so they tell us nothing about position or changes in position.
How else would you describe them and still make correct predictions about experimental results?
As Richard Feynman once said, "quantum mechanics was not wished upon us by theorists". Physicists did not make up all this math about wave functions just for funsies. They were forced to do it in order to make correct predictions about experimental results involving atoms and subatomic particles. Nobody has found any other way to do that; that's why QM is still our best current theory for describing such things.
Measurements of charge are basically measurements of energy: how much energy a given charged particle picks up or loses as it passes through an EM field with particular defined properties.
Dadface said:I'm getting the impression that you're not reading my comments properly.
Dadface said:is there a change of position, albeit indefinite?
Dadface said:When the hydrogen atom is ionised does the does the most probable separation between the proton and electron increase?
Dadface said:I agree that the energy of the atom changes but this energy can be equated, in part, to the change of potential energy of the atom
Dadface said:All I want to know here is does the mathematical description accommodate measured properties.
Dadface said:If so a reference would be useful.
Dadface said:In certain versions of Millikan's experiment charge is measured by observing charged oil drops which are either at rest or moving with constant velocity in a uniform electric field.
PeterDonis said:for any state except the ground state, the radial wave functions have multiple peaks, so the idea that there is a single "most probable separation" is no longer really a good way of looking at it anyway.
PeterDonis said:I'm reading them. I'm just trying to point out to you that you are asking questions that don't have well-defined answers. I suspect you are being misled because you are using ordinary language instead of math. See below.
What does this even mean? Or, to put it another way, can you rephrase this question using math instead of ordinary language?
When the hydrogen atom is ionized the electron isn't bound at all; it's just the proton left.
I suspect what you meant to ask is, when the hydrogen atom is put in an excited state does the most probable separation between the proton and the electron increase? I think the answer to that, if you are comparing to the ground state, is, AFAIK, always going to be yes, but I'm not positive; I would have to take a look at the actual radial wave functions. Note that, for any state except the ground state, the radial wave functions have multiple peaks, so the idea that there is a single "most probable separation" is no longer really a good way of looking at it anyway.
In any case, you cannot generalize the above to a statement that any excited state with higher energy must have a larger most probable separation than all the states with lower energy.
Only if you actually measure it. Otherwise no, you cannot split the energy into a part that's potential energy and a part that's other kinds of energy. You can only say that the atom has some particular energy, corresponding to the stationary state it is in.
Huh? Of course it does.
Um, any QM textbook? Have you looked at one?
Quite honestly, this is such a basic part of QM that I am flabbergasted to see this question even being asked. If QM didn't accommodate measured properties, how in the world do you think physicists would have been able to confirm its predictions in experiments?
Yes, but those are oil drops, not electrons. An oil drop is a macroscopic object, and the classical approximation works fine for them. In the classical approximation, there is no problem assigning a definite position and velocity to the oil drop.
vanhees71 said:Well, you cannot ask a question in theoretical physics, forbid the people you ask to use the adequate language, which is math, and then expect a sensible answer.
The features of "particles" you list as being defined in the standard model is part of the answer: In the standard model you have particle interpretations for asymptotic free states only. To interpret interaction processes as acting forces and accelerating particles as in classical mechanics is at least problematic if not impossible. I tend to think it doesn't make sense since particle interpretations of transient states don't make sense.
In a hydrogen atom of course proton and electron are entangled, but of course you can define sensible quantities to characterize its properties. Among them are statistical quantities like the mean distance between proton and electron, its standard deviation etc.
Dadface said:I'm struggling to express the question in terms of mathematics
Why not? Position, speed and acceleration are observables in QM, too, and the squared wavefunctions in the respective representations yield the probabilities to observe a given position, speed or acceleration.Nugatory said:For bound electrons (the ones that move from one energy state to another in an atom) it makes no sense to talk about their position, speed, or acceleration.
DrDu said:Position, speed and acceleration are observables in QM
If you take an electron in the ground state of the Hydrogen atom and measure its total angular momentum you get 0 with 100% probability.Delta2 said:I don't understand. In quantum physics the electron is a point particle (true or false?). So it arises the question how does it move? Does it move like a point particle along a curved path (mith multiple zig zags e.t.c) which we just can't determine (because we don't have yet the appropriate theory) and so we can speak only with probabilities about its location and movement? Or what does it hold about the movement of electron in the regime of quantum physics?
Some things don't seem to make sense in quantum mechanics. I am sure you ll tell me that they don't make "classical" sense but they make "quantum mechanical" sense. Seems to me one has to redefine fundamental concepts such as the concept of movement in order for QM to make sense.PeroK said:If you take an electron in the ground state of the Hydrogen atom and measure its total angular momentum you get 0 with 100% probability.
The expected value of its kinetic energy is, however, non zero.
What sort of orbit is that, you might ask? Well, it's a quantum mechanical "orbit", which cannot be reasonably explained in classical terms. In particular, in this system it makes little sense to think of the electron "moving" at all.
Delta2 said:Seems to me one has to redefine fundamental concepts such as the concept of movement in order for QM to make sense.
No there isn't anything in the math about movement, but somethings just don't make sense. Like we talk about position and momentum in HUP, but a particle doesn't have definite position and velocity and it is like we are forbidden to talk about its "movement". How does this makes sense to you I don't know but it doesn't seem to make sense to me. Maybe you understand it as the particle being simultaneously in many places with a different probability in each place. But this understanding certainly doesn't make classical sense, might make quantum mechanical sense though.PeterDonis said:And if you can point to something in the math that you think deserves to be called "movement" and give a good argument, you might get such a redefinition accepted. But you're not going to do it by just saying "seems to me".
Delta2 said:we talk about position and momentum in HUP
Delta2 said:this understanding certainly doesn't make classical sense
Yes, electrons always accelerate when transitioning between energy states. This is because when an electron absorbs or emits energy, it changes its velocity and therefore accelerates.
Electrons transition between energy states by either absorbing or emitting energy in the form of photons. This can happen through processes such as absorption, emission, or scattering.
The amount of acceleration during electron energy state transitions is determined by the difference in energy between the initial and final states. The greater the difference in energy, the greater the acceleration.
No, electrons cannot transition between energy states without accelerating. This is because the process of transitioning between energy states involves a change in velocity, which is a form of acceleration.
No, not all electrons transition between energy states at the same rate. The rate of transition depends on the specific energy level and the amount of energy being absorbed or emitted. Additionally, external factors such as temperature and pressure can also affect the rate of transition.