What Stabilizes The Electron Orbit In An Atom?

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
It is well known that a charged particle following a curved path will emit "synchrotron" radiation which is the result of the centrifugal acceleration of the particle.

So why don't the electrons orbiting the nucleus of an atom lose energy by radiation and eventually fall into the nucleus? Obviously, the electrons are held in orbit by the electric field which provides the centripetal force and this field must be relatively constant to maintain the average radius of the orbit.

I found this question in a chemistry book, however, the answer it gave is rather obscure so that's why I posted it here..
 

MrChips

Joined Oct 2, 2009
27,106
It is well known that a charged particle following a curved path will emit "synchrotron" radiation which is the result of the centrifugal acceleration of the particle.

So why don't the electrons orbiting the nucleus of an atom lose energy by radiation and eventually fall into the nucleus? Obviously, the electrons are held in orbit by the electric field which provides the centripetal force and this field must be relatively constant to maintain the average radius of the orbit.

I found this question in a chemistry book, however, the answer it gave is rather obscure so that's why I posted it here..
What is the date of that chemistry book? You are conceptualizing an atom using an old classical mechanical model of electrons orbiting a nucleus. That concept is long outdated.

Why do electrons not fall into the nucleus?
 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
What is the date of that chemistry book? You are conceptualizing an atom using an old classical mechanical model of electrons orbiting a nucleus. That concept is long outdated.

Why do electrons not fall into the nucleus?
I just looked at that page and the answer is very theoretical (mathematical rather than conceptual). If the electron is losing energy because of synchrotron radiation, the loss must be made up from another source, otherwise the atom would collapse.

However, there must be a better way of explaining this process without resorting to exotic jargon like "infinitely negative" or "infinitely positive" potential energy
 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
Electrons do not "orbit" around the nucleus. It does not lose energy because of synchrotron radiation.
OK, so if the electrons do NOT "orbit" the nucleus, then what kind of circular motion do they have? I understand that the path of electrons in an atom involves a wave motion and the radius of the path can assume only certain values. So if the electrons are moving in a curved path (anything other than a straight line) why DON'T they generate synchrotron radiation and lose energy?

In the case of a simple hydrogen atom, it seems that an electron could lose enough energy and eventually crash into the nucleus.
 

Papabravo

Joined Feb 24, 2006
19,253
The way to visualize electrons around a nucleus is to think of them as probability clouds. Any individual electron has a high probability of being located in a particular cloud described by it's principal quantum numbers. The more accurately we determine it's position, the less accurately we know it's momentum. Momentum is a vector quantity with both magnitude and direction. The conundrum of understanding quantum mechanics is the following simple proposition:
  1. If we know where it is, we don't know how fast it is moving and in which direction, therefore we don't know where it is going to be.
  2. If we know it's momentum, then we have no idea where it is and in fact it could literally be anywhere.
Look -- no mathematics, and no matter what you do you cannot pierce the veil -- so stop trying.
There is no requirement for electrons to move along a path of any kind.
 

MrAl

Joined Jun 17, 2014
9,519
Hi,

One way to visualize it might be as follows..

You have a round regular bucket with slanted walls that slant outward toward the open top.
You throw a marble inside the bucket in a trajectory that once it hits the inside wall near the top of the bucket it follows the wall around and around, and as it rotates it looses energy until it gets to the bottom. Given no friction on the walls, once it gets to the bottom of the bucket it will continue to follow the bucket walls forever but also staying at the bottom forever. The marble rotates at the bottom forever because there's no place else to go. If we introduce more energy we can get the marble to start to move up the wall, but for the lack of that extra energy input, the thing will rotate only at the bottom.
The bottom in this case would be the ground state and once it reaches there it has no place else to go unless we force something to happen, which means we introduce energy. There's no energy lost either because there's no friction. There is a well known equation in quantum mechanics that tells us that once it reaches the ground state orbit there is no lower state available so there can be no release of energy.

Another abstract view is a lossless transmission line. If the output connects to the input and there is energy introduced, that energy will rotate around the path of the line forever.

There are many things in nature that exhibit lossless movement. A spinning top in space is another example. Obviously there is angular motion yet it does not stop rotating unless acted on by an outside force, which again is extra energy of some kind. These systems are rotational inertial systems and they have similar properties to linear systems which travel in a straight line. The bottom line to all of this is conservation of energy.
 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
The way to visualize electrons around a nucleus is to think of them as probability clouds. Any individual electron has a high probability of being located in a particular cloud described by it's principal quantum numbers. The more accurately we determine it's position, the less accurately we know it's momentum. Momentum is a vector quantity with both magnitude and direction. The conundrum of understanding quantum mechanics is the following simple proposition:
  1. If we know where it is, we don't know how fast it is moving and in which direction, therefore we don't know where it is going to be.
  2. If we know it's momentum, then we have no idea where it is and in fact it could literally be anywhere.
Look -- no mathematics, and no matter what you do you cannot pierce the veil -- so stop trying.
There is no requirement for electrons to move along a path of any kind.
So what causes the wave motion of an electron? It has mass and there must be some kind of "elastic" force to create oscillation.
Hi,

One way to visualize it might be as follows..

You have a round regular bucket with slanted walls that slant outward toward the open top.
You throw a marble inside the bucket in a trajectory that once it hits the inside wall near the top of the bucket it follows the wall around and around, and as it rotates it looses energy until it gets to the bottom. Given no friction on the walls, once it gets to the bottom of the bucket it will continue to follow the bucket walls forever but also staying at the bottom forever. The marble rotates at the bottom forever because there's no place else to go. If we introduce more energy we can get the marble to start to move up the wall, but for the lack of that extra energy input, the thing will rotate only at the bottom.
The bottom in this case would be the ground state and once it reaches there it has no place else to go unless we force something to happen, which means we introduce energy. There's no energy lost either because there's no friction. There is a well known equation in quantum mechanics that tells us that once it reaches the ground state orbit there is no lower state available so there can be no release of energy.

Another abstract view is a lossless transmission line. If the output connects to the input and there is energy introduced, that energy will rotate around the path of the line forever.

There are many things in nature that exhibit lossless movement. A spinning top in space is another example. Obviously there is angular motion yet it does not stop rotating unless acted on by an outside force, which again is extra energy of some kind. These systems are rotational inertial systems and they have similar properties to linear systems which travel in a straight line. The bottom line to all of this is conservation of energy.
However, the marble is not an electron (and it does not have any charge) and even in a frictionless situation, it can't loose energy by synchrotron radiation. However, an electron can lose energy by synchrotron radiation and it will eventually get close enough to the protons and wind up getting captured.
 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
An electron can behave as either a discrete particle or an electromagnetic wave -IE- the Debroglie Wave.

According to this interpretation, is the "electron" in an atom an electromagnetic wave that travels around the nucleus or a discrete particle? According to the Schrodinger equation, the electron is actually an electromagnetic wave instead of a particle. Therefore, the wave will not lose energy by synchrotron radiation and it will persist forever.

I'm doing more research on the particle/wave duality which will be posted later
 

nsaspook

Joined Aug 27, 2009
10,405
An electron can behave as either a discrete particle or an electromagnetic wave -IE- the Debroglie Wave.

According to this interpretation, is the "electron" in an atom an electromagnetic wave that travels around the nucleus or a discrete particle? According to the Schrodinger equation, the electron is actually an electromagnetic wave instead of a particle. Therefore, the wave will not lose energy by synchrotron radiation and it will persist forever.

I'm doing more research on the particle/wave duality which will be posted later
One of the main reasons for "inventing" quantum mechanics was exactly this conundrum.
https://physics.stackexchange.com/q...drogens-electron-pulled-into-the-nucleus?lq=1

 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
If an electron in an atom is actually an electromagnetic wave instead of a particle, what do the diagrams of electron orbitals indicate?

Also, how is the wave attracted to the protons like a negative particle is attracted to the positive protons?
 

Papabravo

Joined Feb 24, 2006
19,253
If an electron in an atom is actually an electromagnetic wave instead of a particle, what do the diagrams of electron orbitals indicate?

Also, how is the wave attracted to the protons like a negative particle is attracted to the positive protons?
"it's a candy mint" "No, it's a breath mint" "It's two mints in one"
Just like the old Certs commercial, the electron exhibits a duality of behaviors including both particle and wave.
I'm not sure which diagrams you are referring to, but a two dimensional drawing is used to keep track of the quantum numbers in the shells as they fill up, as you move through the periodic table.
The three dimensional drawings are a representation of the probability clouds that define regions of high probability for the location of an electron with a particular set of quantum numbers. Just because there is a high probability of finding it there does not mean it is actually there. As we said, it is not possible to nail down the position or define the path of a bound electron.

 

MrChips

Joined Oct 2, 2009
27,106
If an electron in an atom is actually an electromagnetic wave instead of a particle, what do the diagrams of electron orbitals indicate?

Also, how is the wave attracted to the protons like a negative particle is attracted to the positive protons?
Electrons don't orbit around the nucleus. There are no orbits in the classical sense like planets orbiting the sun. Those orbital diagrams are from an era before quantum mechanics was invented.

Get it out of your system.

Electron orbital is a concept that is based on probability theory. You will not be able to locate an electron in a certain orbit around the nucleus because it is a wave, a cloud, a halo, an aura. People could not wrap their heads around this a hundred years ago. That is why quantum mechanics was invented in order to understand nuclear physics.

I bet you didn't read the article I posted in post #2.
 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
If the De Broglie wave length represents one electron in the particle scattering experiment, then one De Broglie wave length is also equivalent to one electron in an atom.

Therefore, in a hydrogen atom with one electron, one De Broglie wave length is wrapped around the nucleus. So it seems that the wave length/electron whatchamacallit must occupy the entire circular path around the nucleus.

In other words, the single electron is "everywhere" along a circular path around the nucleus. So how can electrons be represented as discrete particles in a circular pattern as they are shown in chemistry and physics books?
 
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MrChips

Joined Oct 2, 2009
27,106
If the De Broglie wave length represents one electron in the particle scattering experiment, then one electron also equals one De Broglie wave length in an atom.

Therefore, in a hydrogen atom with one electron, one De Broglie wave length is wrapped around the nucleus. So it seems that the wave length/electron whatchamacallit must occupy the entire circular path around the nucleus.

In other words, the single electron is "everywhere" along a circular path around the nucleus. So how can electrons be represented as discrete particles in a circular pattern as they are shown in chemistry and physics books?
You are referring to the Bohr model of the atom. Note the word "model".

Modern Atomic Theory
 

MrAl

Joined Jun 17, 2014
9,519
If the De Broglie wave length represents one electron in the particle scattering experiment, then one De Broglie wave length is also equivalent to one electron in an atom.

Therefore, in a hydrogen atom with one electron, one De Broglie wave length is wrapped around the nucleus. So it seems that the wave length/electron whatchamacallit must occupy the entire circular path around the nucleus.

In other words, the single electron is "everywhere" along a circular path around the nucleus. So how can electrons be represented as discrete particles in a circular pattern as they are shown in chemistry and physics books?
Hi,

The Bohr model shows a conceptional idea of what the electrons were believed to be doing. Since they dont actually rotate, it's not exactly correct. However, it is able to represent the energy levels. More advanced chem books will show electron clouds with various configurations.

When i say they dont actually rotate, maybe a better way to put it is they dont actually move. They dont actually move in the wave view because it is a standing wave.

A probability is a little different concept than something considered to be actually moving. When something moves, it starts from one place and gets to another place eventually. That implies some sort of sequential action. A probability is a little different because it's almost as if the electron was everywhere at the same time. I is almost like it is everywhere at least until we observe it. Once we do that it's position becomes fixed. Until then though there is no way to pinpoint the location at the point in time we want to check for it.

Imagine you could somehow see inside the atom without affecting any electrons or clouds, and lets say that the electron is believed to be within some sphere of radius R from the center. Now lets say that your test point is at a fixed point within that sphere, maybe near the radius and say to the right at the point x1,y1,z1. The point is fixed, and we must specify a time when we will look for it, so lets just say time t1. This gives us a point inside and a time so we now have t1,x1,y1,z1.
Now we begin the experiment by taking a snapshot of what is at that point and at that time t1. We may not see the electron at that time and place, and so we record a zero (0) for that time and place. The next time we look however, t2, we may see it at that place and s we record a one (1). IF we do this enough times, we can build up a probability of how likely it would be to find it at that place.
If we move the place to x2,y2,z2, we'll get another probability, and if we do this in many different places we'll see a shape begin to form where the more frequent finds could be colored a darker color.
When we look at this picture from afar though, it appears to be one solid object that is not moving but just 'exists' like that.
I guess there is a lot too this though if you really want to dig deeper.
 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
So the De Broglie electromagnetic wave in an atom is actually a standing wave instead of a traveling wave?

Then, how does the electron wave actually absorb energy from an outside source such as a photon? The photon must raise the electron one quantum state -IE- the next level up.

Also, is an electron in the conduction band (the band just above the valence band with a gap in between) considered as bound to the atom and subject to quantum mechanics?
 

nsaspook

Joined Aug 27, 2009
10,405
If you think of electrons as standing waves then there are whole number nodes were energy states (excited levels) are possible.
https://www.physicsforums.com/threa...an-electron-gains-energy.682292/#post-4329917

The problem is this (de Broglie electron standing waves) only really works for Hydrogen to explain energy levels so you need QM (quantum wave functions) to explain the rest of the atoms.

The electron has a ground (base) state. If an electron is in an energy state higher than its lowest (base) state then it is not stable and it's possible for it to fall back to the ground state and emit a photon.
The orbitals are not PLACES, they are EINGEN STATES ("characteristic") of energy.
http://www.grandinetti.org/quantum-theory-matter
 

Thread Starter

Glenn Holland

Joined Dec 26, 2014
705
If the electron in an atom is a wave, then how does it get a negative charge so it is attracted to the necleus?

Then when a free electron is outside of an atom (such as in an ionized gas or in a vacuum), is it a discrete particle instead or a wave?
 

crutschow

Joined Mar 14, 2008
30,758
As long as you keep trying to visualize what is physically happening in the quantum world you will remain largely confused.
The quantum world is described by mathematical functions of waves and probability that do not readily correspond to what we see and understand in our macro physical world.

For example in the two slit experiment a series of single electrons can go through both slits at the same time, generating a wave-like interference pattern on a target behind the slits, if they are not observed.
If they are observed in some manner to determine where they landed, even after going through a slit, then there is no interference pattern, indicating they went through one slit at a time like a particle.
So the electron behaves as a wave if you don't observe it, and behaves as a particle if you observe it.
I don't know of any way that it's possible to visualize how that happens. :rolleyes:
You just have to accept, that's how the quantum world operates.
 
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