Easy question: why don't electrons spin into the nucleus?

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  • #1
brum
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ive read the answer so many times, i just can't think of the reason now...

since the protons are positive and the electrons are negatively charged, why don't the electrons simply fall into the nucleus?
 
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  • #2
quantumdude
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Electrons bound in atoms are described by standing wavefunctions that occupy nonradiating states, as opposed to the classical model according to which an electron should radiate energy and spiral into the nucleus.

Is that what you are looking for?
 
  • #3
brum
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yeah thanks

but, how would the electron "radiating energy" cause it to spiral into the nucleus as opposed to the other option---"nonradiating states"?

in other words, can you briefly explain each of these 2 cases. thanks
 
  • #4
Classically you would have electrons orbitting the nucleus in ellipses -- just like planets and the sun. Except accelerating/orbitting charges radiate light, losing energy, and would spiral into the nucleus. That what you wanted, or was it why an accelerating charge radiates?
 
  • #5
Originally posted by Tom
Electrons bound in atoms are described by standing wavefunctions that occupy nonradiating states, as opposed to the classical model according to which an electron should radiate energy and spiral into the nucleus.

Is that what you are looking for?

If there is a proton around, it will attract an electron and cause it to accelerate, so how does an electron occupy a non-radiating state inside an atom?
 
  • #6
drag
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Greetings !
Originally posted by Eyesee
If there is a proton around, it will attract an electron and cause it to accelerate, so how does an electron occupy a non-radiating state inside an atom?
Like Tom said - "Electrons bound in atoms are
described by standing wavefunctions that occupy
nonradiating states ".
These "states" are called Orbitals. Orbitals, unlike
orbits, are symmetric clouds passing through the
nucleus (with their sharper edges - like water drops
connected). The Pauli Exclusion Principle is the result
of QM calculations and it determines that no more
than two electrons can occupy every orbital.

"Does dice play God ?"

Live long and prosper.
 
  • #7
Originally posted by drag
Greetings !

Like Tom said - "Electrons bound in atoms are
described by standing wavefunctions that occupy
nonradiating states ".
These "states" are called Orbitals. Orbitals, unlike
orbits, are symmetric clouds passing through the
nucleus (with their sharper edges - like water drops
connected). The Pauli Exclusion Principle is the result
of QM calculations and it determines that no more
than two electrons can occupy every orbital.

"Does dice play God ?"

Live long and prosper.

Hi,

Ok, let's take the hydrogen atom for example. It has one electron and one proton. If protons and electrons attract, what keeps the electron away from the proton?
 
  • #8
FZ+
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Quantised energy levels for the orbiting electron.
 
  • #9
NEOclassic
163
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Frienly tutorial

Originally posted by drag


Like Tom said - "Electrons bound in atoms are
described by standing wavefunctions that occupy
nonradiating states ".
These "states" are called Orbitals. Orbitals, unlike
orbits, are symmetric clouds passing through the
nucleus (with their sharper edges - like water drops
connected). The Pauli Exclusion Principle is the result
of QM calculations and it determines that no more
than two electrons can occupy every orbital.

Hi Drag,
FYI: You have it a little backward because the
QM calculations are the result of the Pauli principle and
that principle was the result of the classic discovery, by dint
of the characteristic x-ray spectrum, that showed, experimentally,
the significant difference between k-a and k-b radiations.
Furthermore, the Pauli principle does not merely limit an orbital to two electrons but demands that they must differ in some trait other than the similarity of their charges. QM may very well assume that inertial spin – up vs. down – is a sufficient difference; however. because charge and mass are intrinsically coupled and further, because dipolar spin is markedly feebler than dipolar magnetism, the classic modeling prefers the strong attractiveness of the latter.

It is apparent to me that your reference to “clouds passing through the nucleus” suggests that drawings found in chemistry texts, that look like balloons and dumbbells, have been mistakenly interpreted by you as representing some kind of orbital property. In reality, those drawings represent the probability of the position/momentum paradox associated with single (usually orbitally uncoupled valence) electrons that are used to demonstrate concerning the uncertainty indicated by Heisenberg. [E.g. the nitrogen atom has three valence electrons and a drawing of that atom would show three independent orthogonally disposed dumbbells. When ammonia gas is formed, by three covalent bonding quantum orbitals, the so-called hydrogen bonds remain orthogonally disposed.]

Your audience is appreciated. Thanks, Only The Messenger
 
  • #10
teddy
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I think what you are looking for is this:

the minimum average distance between an electron and the proton is limited by Heisenberg's uncertainity principle.the electron must have a zero point energy for consistency of HUP. this will be violated in case electron falls into the nucleus.
this is analogous to the 'fermi pressure' in case of neutron stars not collapsing under gravitation.
 
  • #11
quantumdude
Staff Emeritus
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Originally posted by Eyesee
If there is a proton around, it will attract an electron and cause it to accelerate, so how does an electron occupy a non-radiating state inside an atom?

I think the problem is in the sentence above.

Electrons do not have well-defined trajectories, such as those we are accustomed to in everyday life. Thus, we do not speak of a position function x(t) for the electron. Since acceleration is just the second time derivative x''(t) of position, we do not speak of that for quantum particles, either.
 
  • #12
Hi,

the HUP places a limit on measurement of the states of the proton and the electron but I don't see how that principle can force the electrons from falling into the proton nucleus of a hydrogen. Isn't that like saying because I am blind, the electron won't be attracted by the proton?

Is there some other stuff in the hydrogen atom besides the electron and proton?
 
  • #13
quantumdude
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The HUP does not acquire its physical importance from the process of measurement, so your blindness has nothing to do with it. HUP bears on the problem because it is a consequence of the fact that the electron is a standing wave inside the atom. Standing waves can only exist at discretely defined energies, and in the case of atoms, E=0 is not one of them.
 
  • #14
Originally posted by Tom
The HUP does not acquire its physical importance from the process of measurement, so your blindness has nothing to do with it. HUP bears on the problem because it is a consequence of the fact that the electron is a standing wave inside the atom. Standing waves can only exist at discretely defined energies, and in the case of atoms, E=0 is not one of them.

Hi,

thx, that makes more sense. Is the electron like stretched out into a closed loop inside an atom and the loop is oscillating?
 
  • #15
bogdan
191
0
The electron is described by a probability function...it's a function that depends on space...and it's value is a complex number (a+ib)...the integral of the "modulus"(translation) of this function over the entire space must be 1;
the value of the function is the amplitude of probability;
the "modulus" (sqrt(a^2+b^2)) is the probability that the particle is located at that "x"...so...you see...there's no "physical" wave...like an oscillator...
 
  • #16
Originally posted by bogdan
The electron is described by a probability function...it's a function that depends on space...and it's value is a complex number (a+ib)...the integral of the "modulus"(translation) of this function over the entire space must be 1;
the value of the function is the amplitude of probability;
the "modulus" (sqrt(a^2+b^2)) is the probability that the particle is located at that "x"...so...you see...there's no "physical" wave...like an oscillator...

Hi,

now I'm confused again. Someone just said that the electron is actually a standing wave inside the atom and that is why they don't fall into the nucleus. It seems you are now arguing again it is the probability function, i.e. a consequence of the HUP that prevents the electron from falling into the nucleus.

A hydrogen atom only has a proton and an electron- if opposite charges simply attract each other, what keeps them apart besides a probability function?
 
  • #17
Hi, now I'm confused again.
Welcome to the world of quantum mechanics! :wink:

First, do you get the classical picture of how the electron doesn't fall into the nucleus? Same reason the Earth doesn't fall into the sun: it's orbitting around it.

In QM, it's sort of similar. Except an electron isn't really a particle, but a wavefunction, which is like a probability wave -- a standing wave if it's bound in an atom. This has a minimum energy, which gives the 'closest' orbit it can be in around the nucleus. But, when you look for the electron, you always find it in one place, with its probability given by the amplitude of its wavefunction (squared).
 
  • #18
STAii
333
1
Originally posted by damgo
First, do you get the classical picture of how the electron doesn't fall into the nucleus? Same reason the Earth doesn't fall into the sun: it's orbitting around it.
Umm ... not the same.
The electron is electrically charged, the moon is not.

Sometimes you find the answers where you don't expect them.
See this PF topic
 
  • #19
quantumdude
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Science Advisor
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Originally posted by STAii
Umm ... not the same.
The electron is electrically charged, the moon is not.

It is close enough.

The electron is electrically charged, and it the electric force that keeps it in orbit.

The moon is "gravitationally charged" (IOW, it has mass), and it is the force of gravity tht keeps it in orbit.
 
  • #20
STAii
333
1
I know Tom, this is not what i meant.
What i meant is that an moving electrically charged body will produce an electromagnetic wave (well, at least this is what they thought to be always true in the old days), while a moving gravitationally charged body will not produce any kind of wave that may take energy from it (at least not till the theories of today, and not till we find clues of Gravitons).
 
  • #21
Actually they will... gravitational waves! Decays of binary star systems have been observed, and the rate matches that predicted for energy loss via gravitational radiation. However, gravitational waves are suppressed to a greater degree than EM waves: only the quadrupole and greater moments survive. To a first approximation, the power loss for a slow two-body system is P~2/5 * G^4 * M^5 / r^5. Most GR books derive this; also the first decaying system observed was PSR1913+16 and Hulse&Taylor got a Nobel in 1993 for finding it.
 
  • #22
STAii
333
1
You need gravitons to have gravitational waves ... right ?
And ... we didn't proove the existence of gravitons yet ... right ?
 
  • #23
Naaa, it's a complete classical GR effect. Just like you don't need to know about photons to study EM waves.
 
  • #24
brum
81
0
the Earth is being pulled towards the sun by the sun's gravity


so, wouldn't that be like one of those round curved things at museums where you put a penny in on the side and the penny slides around and around and around and around and faster and faster and closer to the center ... because it curves towards the center (a hole) and so the penny gradually comes to the center, gets faster and faster, and then drops down the hole

or does the massive velocity of the Earth help to keep it from falling in towards the sun?

exactly what causes it from falling into the sun?
and i guess the same goes for the moon to Earth, etc.

edit: couple typos

it just seems to me that since spacetime is curved, the satellite (earth, moon, whatever) naturally falls into the source of the gravity
 
  • #25
drag
Science Advisor
1,100
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Greetings NEOclassic !
Originally posted by NEOclassic
Hi Drag,
FYI: You have it a little backward because the
QM calculations are the result of the Pauli principle and
that principle was the result of the classic discovery, by dint
of the characteristic x-ray spectrum, that showed, experimentally,
the significant difference between k-a and k-b radiations.
Furthermore, the Pauli principle does not merely limit an orbital to two electrons but demands that they must differ in some trait other than the similarity of their charges. QM may very well assume that inertial spin – up vs. down – is a sufficient difference; however. because charge and mass are intrinsically coupled and further, because dipolar spin is markedly feebler than dipolar magnetism, the classic modeling prefers the strong attractiveness of the latter.

It is apparent to me that your reference to “clouds passing through the nucleus” suggests that drawings found in chemistry texts, that look like balloons and dumbbells, have been mistakenly interpreted by you as representing some kind of orbital property. In reality, those drawings represent the probability of the position/momentum paradox associated with single (usually orbitally uncoupled valence) electrons that are used to demonstrate concerning the uncertainty indicated by Heisenberg. [E.g. the nitrogen atom has three valence electrons and a drawing of that atom would show three independent orthogonally disposed dumbbells. When ammonia gas is formed, by three covalent bonding quantum orbitals, the so-called hydrogen bonds remain orthogonally disposed.]

Your audience is appreciated. Thanks, Only The Messenger
Thank you for correcting possible misunderstandings
that could arouze from what I wrote. I'm not in any
way an expert in the field. However, of course
that I was talking about probability of finding
the electrons in the orbitals, and I appologize
if I mislead someone by my shortened description.

As for the Pauli Exclusion Principle, I'm not certain
what came first so I'll take your expert word
for it. I would like to ask though :
Doesn't QM "force" the PEP to exist - as a natural
result from the theory (even if that's not the way it
was discovered) ?
Thanks.

"Does dice play God ?"

Live long and prosper.
 
  • #26
Originally posted by damgo
Welcome to the world of quantum mechanics! :wink:

First, do you get the classical picture of how the electron doesn't fall into the nucleus? Same reason the Earth doesn't fall into the sun: it's orbitting around it.

In QM, it's sort of similar. Except an electron isn't really a particle, but a wavefunction, which is like a probability wave -- a standing wave if it's bound in an atom. This has a minimum energy, which gives the 'closest' orbit it can be in around the nucleus. But, when you look for the electron, you always find it in one place, with its probability given by the amplitude of its wavefunction (squared).


Hi,

our solar system has a fixed number of large masses so I can kind of see how the Earth and other planets can reach an equilibrium but it seems that in the atomic world, the system is changing all the time. Gases in the atmosphere for example are moving around all the time. Now, how do electrons reach an equlibrium here? If there were new planets moving in and out of our solar system, I would not expect the orbits of the Earth or any of the planets to be in equlibrium.
 
  • #27
bogdan
191
0
well...the exchange photons and move to new "orbits"...fixed...
 
  • #28
NEOclassic
163
0
Tutorial continued

Originally posted by drag
Greetings NEOclassic !


Doesn't QM "force" the PEP to exist - as a natural
result from the theory (even if that's not the way it
was discovered) ?
Thanks.


Let me explain why classic modeling accepts the like-charge two-electron quantum orbital as intrinsic and as permanent as “forever” unless a given orbital is removed (i.e., decoupled as with the breaking of intra-molecular bonding of atoms where the orbital is only temporary because of the absence of a strong central nuclear field) from the atomic kernel where it would rapidly fly apart becoming two independent free electrons. E.g., consider the single iron atom nested in the four nitrogen atoms centered in the square-planar hemoglobin molecule in your blood; the kernel of that atom – the Argon structure (i.e. excluding the valence electrons which are available for variation of chemical behavior of the iron atom); that particular atom was created somewhere in the heart of the Milky Way, some 6 billion years ago, and after it completes its mission in your blood it remains intrinsically alive forever in the future.
The upshot is that the QM like-charge orbital was the natural property of matter creation. PEP is really only Pauli’s recognition of QM’s intrinsic property. Calling the orbital a “standing wave” because it does not radiate is merely a patch the QED folk use to obfuscate the reality that the orbital is two electrons following each other at high speed that is locked-in permanently. It is true that the “wave nature”, although not radiative, is possibly determined on the basis of the frequency of rotation of the orbital loop. Note: the moving charges of the loop current do cause a magnetic force field normal to the plane of the loop that is exactly countered by the torque caused by the centrifugal force due to angular momentum of the two electron masses. Thanks for your audience. Only the messenger, Jim
 
  • #29
drag
Science Advisor
1,100
1
Greetings NEOclassic !

Thank you for such a full and informative answer
(though I must admit that it's partially "beyond" me).
So, basicly what you're saying is that the answer is yes,
right ?

"Does dice play God ?"

Live long and prosper.
 
  • #30
PLANE AND SIMPLE

F=force
R=distance
the electron doesn't fall on the proton cause FRR has to be constant. if the electron fall anyway then R=0 but F=(+/-)infinity thus the electron becomes highly unstable. On the other hand FdR has to be positive i.e. the force shifts the object it acts upon in the same direction of the force vector. it is the most basic principle of dynamics according to mua. that's what Newton should have said in his second law instead F=ma where the last equation is wrong again according to mua. since F=(+/-)infinity and FdR>0 follows that dR<>0 thus the electron leaves this unstable location right away.
 
Last edited by a moderator:
  • #31


Originally posted by NEOclassic
Let me explain why classic modeling accepts the like-charge two-electron quantum orbital as intrinsic and as permanent as “forever” unless a given orbital is removed (i.e., decoupled as with the breaking of intra-molecular bonding of atoms where the orbital is only temporary because of the absence of a strong central nuclear field) from the atomic kernel where it would rapidly fly apart becoming two independent free electrons. E.g., consider the single iron atom nested in the four nitrogen atoms centered in the square-planar hemoglobin molecule in your blood; the kernel of that atom – the Argon structure (i.e. excluding the valence electrons which are available for variation of chemical behavior of the iron atom); that particular atom was created somewhere in the heart of the Milky Way, some 6 billion years ago, and after it completes its mission in your blood it remains intrinsically alive forever in the future.
The upshot is that the QM like-charge orbital was the natural property of matter creation. PEP is really only Pauli’s recognition of QM’s intrinsic property. Calling the orbital a “standing wave” because it does not radiate is merely a patch the QED folk use to obfuscate the reality that the orbital is two electrons following each other at high speed that is locked-in permanently. It is true that the “wave nature”, although not radiative, is possibly determined on the basis of the frequency of rotation of the orbital loop. Note: the moving charges of the loop current do cause a magnetic force field normal to the plane of the loop that is exactly countered by the torque caused by the centrifugal force due to angular momentum of the two electron masses. Thanks for your audience. Only the messenger, Jim


What is a "Qm like-charge orbital"?
 
  • #32
NEOclassic
163
0


Originally posted by Eyesee
What is a "QM like-charge orbital"?

Hi Eyesee,

QM means Quantum Mechanics, which is that branch of physics that deals with the nature of those many electrons that surround an atomic nucleus. Because valence electrons are not paired up (until stable molecules happen that form quantum pairings that chemists call “bonds” that are actually extra-nuclear quantum-orbitals) they do not behave in the orbital manner of the non-valence “kernel-orbitals”. While a single electron charge could easily move in a loop, its intrinsic buddies, mass and spin, present a problem in stabilizing that loop (as with a play-ground teeter-totter); so nature demands a balancing mass be inserted diametrically opposite which completes the quantum orbital. Or does it? Didn’t Pauli postulate that something else was necessary to overcome the electrostatic repulsion of the two like-charges in the loop? To early classic physicists spin-flip was the obvious answer until someone observed that the balance of spin inertia, while important in a minor way, was much too feeble to overcome electrostatic repulsion. All that was therefore available was a different view of the novel electrodynamic notion that the intrinsically spinning charge of each electron rendered it a small dipolar “bar-magnet” which was extremely attractive to its neighbor when spin-flipped. The reason why I refer to the two negative electrons in the loop as a “like-charged orbital” is because of the revelation, discovered in the thirties, that in the electron/positron delayed annihilation process, the opposite-charges of the electrons satisfied, per se, the Pauli Exclusion Principle, thus freeing the magnetic spin orientations as a matter of arbitrary selection. [That’s why there are two differing positroniums, singlet and triplet.]

Incidentally, a survey of all the proton/deuteron/etc fragments discovered at the World’s atom smashers shows that all except photons, electrons and positrons decay in extremely short times to those three entities; important among the unstable particles is the only one smaller than the mu-meson which is called positronium.

Until this “unlike-charged orbital” is postulated as QM’s mass-enhanceable sub-nucleonic building block, the current Standard Model will likely continue to be fatally flawed. Thanks for your audience, Only The Messenger – Jim.

"Logic is easy when done Nature's way."
 
  • #33


Originally posted by NEOclassic
Hi Eyesee,

QM means Quantum Mechanics, which is that branch of physics that deals with the nature of those many electrons that surround an atomic nucleus. Because valence electrons are not paired up (until stable molecules happen that form quantum pairings that chemists call “bonds” that are actually extra-nuclear quantum-orbitals) they do not behave in the orbital manner of the non-valence “kernel-orbitals”. While a single electron charge could easily move in a loop, its intrinsic buddies, mass and spin, present a problem in stabilizing that loop (as with a play-ground teeter-totter); so nature demands a balancing mass be inserted diametrically opposite which completes the quantum orbital. Or does it? Didn’t Pauli postulate that something else was necessary to overcome the electrostatic repulsion of the two like-charges in the loop? To early classic physicists spin-flip was the obvious answer until someone observed that the balance of spin inertia, while important in a minor way, was much too feeble to overcome electrostatic repulsion. All that was therefore available was a different view of the novel electrodynamic notion that the intrinsically spinning charge of each electron rendered it a small dipolar “bar-magnet” which was extremely attractive to its neighbor when spin-flipped. The reason why I refer to the two negative electrons in the loop as a “like-charged orbital” is because of the revelation, discovered in the thirties, that in the electron/positron delayed annihilation process, the opposite-charges of the electrons satisfied, per se, the Pauli Exclusion Principle, thus freeing the magnetic spin orientations as a matter of arbitrary selection. [That’s why there are two differing positroniums, singlet and triplet.]

Incidentally, a survey of all the proton/deuteron/etc fragments discovered at the World’s atom smashers shows that all except photons, electrons and positrons decay in extremely short times to those three entities; important among the unstable particles is the only one smaller than the mu-meson which is called positronium.

Until this “unlike-charged orbital” is postulated as QM’s mass-enhanceable sub-nucleonic building block, the current Standard Model will likely continue to be fatally flawed. Thanks for your audience, Only The Messenger – Jim.

"Logic is easy when done Nature's way."


Hi,

very nice explanation. You are saying that it is the different spins of the electrons in addition to the attractive magnetic field generated by its spinning that stabilizes the electrons inside the atoms? That may well work for multiple electron atoms, but what about the hydrogen atom? Are hydrogen atoms stable in isolation or do their electrons fall into the nucleus? If they are stable then the different spins of the electrons wouldn't explain it, right?
 
  • #34
NEOclassic
163
0
Tutorial continued

Originally posted by Eyesee
Hi,

very nice explanation. You are saying that it is the different spins of the electrons in addition to the attractive magnetic field generated by its spinning that stabilizes the electrons inside the atoms? That may well work for multiple electron atoms, but what about the hydrogen atom? Are hydrogen atoms stable in isolation or do their electrons fall into the nucleus? If they are stable then the different spins of the electrons wouldn't explain it, right?

Hi again I.C.,

What I meant was "that opposite spins of the electrons ARE magnetically attractive as contrasted with parallel spins which are magnetically repulsive."

About the hydrogen atom with its unpaired valence type electron let me direct you to Feynman Notes, Chap 19, Vol. III where indeed his thought-experiment places the single uncoupled electron as subject to the Heisenberg dumbbell shaped probabilities (I think he calls these amplitudes) and which are not visible in the ground state (the magnetic dipoles are coaxial with the electrostatic attraction between proton and electron being countered by the magnetic poles of the two being directed repulsively by like-magnetic poles facing each other) because there must be excitement of the electron in order for Planck incremental photo radiation frequencies to occur. Nature’s lab in the photosphere, chromosphere, corona of the Sun shows a few of the many Planck incremental excitement levels that are referred to as the “Balmer”, “Lyman”, and “Paschen” series.
Feynman’s thought experiment of the H2+ ion is not only quite nervous but is, similar to the H atom, not a quantum coupling, and whose “ground state” involves all three particles as being spin-wise coaxial with the central electron so oriented that like-magnetic poles prevail at each pole of the electron; thus limiting the electro- static tendency toward collapse. Thanks for your audience, Only the Messenger, Jim.

"Logic is easy when done Nature's way."
 

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