Explanation why dosen't the electron fall into the nucleus?

[pivoxa15]

Since the nucleus of an atom is +charged and the electron is -charged, why doesn't at least one electron fall into the nucleus?

 

[Dr.Brain]

Infact you can interpret the sam ein another way. The force that attracts the electron towards the nucleus is the coulomb's force of attraction , therefore when electron is acted upon by this attraction force , it starts falling towards the nucleus in the sense that it keeps failing from taking the straightline path it otherwise would have taken in the absence of external force , thus it on the otherside rotates around the nucleus preserving the minimum quanta of energy it can hold in its state.Since there is a minimum 'quanta of energy' of the atomic orbital the wavefuntion of electron satisfies , it remains in that state and doesnot fall...

 

[pivoxa15]

, thus it on the otherside rotates around the nucleus preserving the minimum quanta of energy it can hold in its state.Since there is a minimum 'quanta of energy' of the atomic orbital the wavefuntion of electron satisfies , it remains in that state and doesnot fall...

That was the explanation given by Bohr but that was not an accurate enough picture because the electron dosen't rotate around the nucleus. Bohr couldn't explain the quantised angular momentum which lead to the quantised energy levels either.

 

[Dr.Brain]

What Bohr couldn't explain was that , accelerating electrons radiate EM rays and lose energy , so why don't they end up losing so much energy that they fall into the nucleus ... the appt. answer was given later when the concept of 'quantised energy' states came into picture. As per this , the elctrons can possesses only some particular quantised energies which are connected with corresponding orbitals , The elctron in first energy state will have some energy which is particular with that atomic orbital , to reach the second shell , the electron should have some other 'bundle of energy' which will be higher than what it would have in the first shell. So due to quantisation , minimum energy an electron in an orbital can possesses would be some finite amount which wouldn't allow it to fall into the nucleus . The electron cannot have energy lower than that 'minimum amount of energy' , which could have allowed it to fall into the nucleus .

BJ

 

[marlon]

Bohr couldn't explain the quantised angular momentum which lead to the quantised energy levels either.

I don't understand. Quantisized L and energy are the basic assumption's of Bohr's model. This models "solves" the problems with electrons spiraling down towards the nucleus because of it's basic assumptions it was built from. This model is "wrong" because it assumes that electrons have circular orbits around the nucleus. This clearly contradicts with HUP. But than again, Bohr's model (from 1913) is about 13 years older than Schrödinger's work.

regards
marlon

 

[cartuz]

Since the nucleus of an atom is +charged and the electron is -charged, why doesn't at least one electron fall into the nucleus?

From history it is known that to this question Born is answers by postulate (or axiom) that electron is not emitting the EM on stationary orbits. It is one of Born's postulates. Later, from quantum theory it is following that the electron is spread on whole orbit around the nuclei because nothing emits EM.
But we can discuss the question. Is it okay with the energy balance of atom in quantum mechanics because we must to consider the relict gravitation fields, I suppose but don't sure.

 

[pivoxa15]

I don't understand. Quantisized L and energy are the basic assumption's of Bohr's model. This models "solves" the problems with electrons spiraling down towards the nucleus because of it's basic assumptions it was built from. This model is "wrong" because it assumes that electrons have circular orbits around the nucleus. This clearly contradicts with HUP. But than again, Bohr's model (from 1913) is about 13 years older than Schrödinger's work.
regards
marlon

I was trying to say that Bohr couldn't come up with a reason why electrons were quantised in orbitals with quantised angular momentum. He just accepted them as axioms if you like.


What I like to know is what is the current conventional reason given to why electrons does not stick to the nucleus. There is obviously an attractive force between them but what is cancelling this attractive force and keeping the electron from totally "falling" into the nucleus?

 

[michael879]

well I know this isn't the answer your looking for, but forgetting all the quantum stuff, in a Newtonian world, the electrons wouldn't all fall into the nucleus either. the ones closer to the nucleus would repel the ones farther away.

 

[dicerandom]

well I know this isn't the answer your looking for, but forgetting all the quantum stuff, in a Newtonian world, the electrons wouldn't all fall into the nucleus either. the ones closer to the nucleus would repel the ones farther away.

If you do the calculation, classically the electron in a hydrogen atom should fall into the nucleus within a small fraction of a second. The same general idea holds for the inner non-screened electrons in any other atom.

 

[michael879]

yea I know, I was just saying in an atom with a lot of electrons, they wouldn't all fall into the nucleus.

 

[Suedeos]

[random]
at post #2..
so it's kinda like how shuttles are in a constant state of freefall around the earth?
[/random]

 

[michael879]

[random]
at post #2..
so it's kinda like how shuttles are in a constant state of freefall around the earth?
[/random]

no... the electrons don't orbit, they can't accelerate because accelerating charges produce light, which would slow the electrons down and they would spiral into the nucleus.

 

[jtbell]

What I like to know is what is the current conventional reason given to why electrons does not stick to the nucleus. There is obviously an attractive force between them but what is cancelling this attractive force and keeping the electron from totally "falling" into the nucleus?

An atomic electron has a quantum-mechanical probability distribution which is much larger than the nucleus. This distribution cannot shrink so that it is completely contained inside the nucleus, because of the Heisenberg uncertainty principle.

Nevertheless, the probability distibution is usually not zero inside the nucleus, so there is a small but nonzero probability that the electron can actually be inside the nucleus. In some isotopes, the nucleus can then "capture" the electron and convert a proton to a neutron. This electron capture process has properties similar to beta+ decay, in which the nucleus emits a positron.

 

[Ratzinger]

When an electron is more confined, it has a higher energy spread. Does that imply it is more energetic than a less confined? If so, why are the higher energy orbitals farther away from the nucleus and confine the electron lesser in space (why are higher orbitals larger in space)?
Edit: but wait, energy is quantised in atoms, so why talking about HUP here?

 

[pivoxa15]

there is a small but nonzero probability that the electron can actually be inside the nucleus.

I appreciate that everything is a probability with the atom. When you were referring to a small probability that the electron is sticking to the nucleus, you were probably assuming when the electron were in n=1 or higher states.

My question is more, why isn't there an electron state with n=0, that is when the electron is most probably in the nucleus. This state would seem to the most natural for an unexcited electron because of the attractive coloumb force that exists between the electron and proton.

 

[jtbell]

There is no solution to the Schrödinger equation for hydrogen with n=0. The quantum number n enters into the radial part of the wave function, which is the messiest part of the solution (associated Laguerre polynomials :yuck: ). I haven't looked at the derivation since grad school, and my QM books are at the office, so all I can do right now is guess that n=0 would give you a wave function which is zero everywhere.

In fact, as I recall (again not having my books handy) the n=1 probability distribution does in fact have its maximum value at the origin, i.e. at the nucleus! However, the probability of being within the nucleus also depends on the volume. The volume of the nucleus is very small, so the probability of being inside the nucleus is also small.

If the probability distribution over a volume is constant, then (probability of being inside that volume) = (value of probability distribution) x (volume). If the probability distribution isn't constant, but doesn't change much, then if you take the average value of the probability distribution, this is still a pretty good approximation.

[Note: I'm leaving town tomorrow and won't be back until after Christmas, so someone else will have to answer any further questions.]

 

[jtbell]

When an electron is more confined, it has a higher energy spread. Does that imply it is more energetic than a less confined? If so, why are the higher energy orbitals farther away from the nucleus and confine the electron lesser in space (why are higher orbitals larger in space)?
Edit: but wait, energy is quantised in atoms, so why talking about HUP here?

Remember, the HUP connects position and momentum. More specifically, it connects corresponding vector components: $x$ with $p_x$, etc. It's quite possible for $p_x$, $p_y$ and $p_z$ to vary (or be uncertain) while the kinetic energy remains constant. Also, the (total) energy includes potential energy, which certainly varies with position for an atomic electron.

So there's no problem with atomic states having a definite fixed energy. What they can't have is a definite fixed momentum.

 

[Dr.Brain]

And as far as I remember the wavefuction of the only electron in Hydrogen atom permits electron being inside the nucleus. That is for r=0 the exponential function converges to zero. Please correct me if anyone knows the exavt wavefunction expression.

BJ

 

[pivoxa15]

According to the textbook, the most probable distance the electron is from the nucleus in the ground state of H is 0.529(10^-10)m

This is very far compared with the diameter of a nucleus which is of the order of (10^-15)m

The question is still what keeps the electron such a far distance away from the nucleus. Surely it would like to be as close as possible to the nucleus.

 

[jtbell]

[I have time for one last word while eating breakfast...]

Oddly enough, in the $n=1$ state of hydrogen, the most probable position of the electron is at the origin (the nucleus), whereas the most probable radius is at the Bohr radius $a_0$! This is not a contradiction because there are many more positions that have $r=a_0$ than have $r=0$. Therefore, even though the probability density (square of the wave function) is larger for $r=0$ than for $r=a_0$, the radial probabilty is larger at $r=a_0$. Note the two different names for the quantities!

For the hydrogen wave functions and probability distributions, click here.

The question is still what keeps the electron such a far distance away from the nucleus.

And my answer is still: the Heisenberg uncertainty principle.

 

[pivoxa15]

[I have time for one last word while eating breakfast...]
Oddly enough, in the $n=1$ state of hydrogen, the most probable position of the electron is at the origin (the nucleus), whereas the most probable radius is at the Bohr radius $a_0$! This is not a contradiction because there are many more positions that have $r=a_0$ than have $r=0$. Therefore, even though the probability density (square of the wave function) is larger for $r=0$ than for $r=a_0$, the radial probabilty is larger at $r=a_0$. Note the two different names for the quantities!
For the hydrogen wave functions and probability distributions, click here.
And my answer is still: the Heisenberg uncertainty principle.

Things are starting to make more sense now. I read somewhere that a physicist said that the reason why we don't fall through a chair is because of the Heisenberg Uncertainty principle. I did not understand that at first but the reason seems to be that the HUP gives reason to why electrons are not at the nucleus. Hence chemical bonds may form between the electrons which in turn makes a chair very stable due to the coulomb force between the atoms.

 

[cartuz]

I was trying to say that Bohr couldn't come up with a reason why electrons were quantised in orbitals with quantised angular momentum. He just accepted them as axioms if you like.
What I like to know is what is the current conventional reason given to why electrons does not stick to the nucleus. There is obviously an attractive force between them but what is cancelling this attractive force and keeping the electron from totally "falling" into the nucleus?

I don't know anybody who answers to this question in literature. But it is clear that it is the minimum of action function S=T-U, where T - kinetic energy, U - potential energy. This minimum is S=h/2pi. We can consider as analog the system of two classical particles in the sphere with non-zero energy. The momentum of this particles is non-zero two. And this particles is not collide because they moving.

 

[Karrar]

Since the nucleus of an atom is +charged and the electron is -charged, why doesn't at least one electron fall into the nucleus?

quantim mechanic say that reason due to duality property >>> so because electron have wave- like particle make the electron gian spread property

but I not statsify,, I thing the same force that make the planet stable in it's orbit ... make the electron stable in it's probablity location ... that's my opinion

 

[ytuab]

I think it's a little old thread.

For example, In the Bohr model, they say when the orbital length is a integer times the de Broglie's wavelength, the electron's movement is stabe and it doesn't fall into the nucleus.

But the probability density of the Shroedinger equation is more complex than the Bohr model. (I wonder why the electron moves so comlexly though the equation of motion indicates the Coulomb force between the nucleus and the electron influences the motion.)

So In QM, they say due to the uncertainty pronciple, the electron is not actually moving and it behaves as an electron cloud...

But If the electron is not actually moving, how can the next phenomina be explained?

If we consider the nuclear movement around the center of mass, and use the reduced mass of an electron, the calculation result of the energy becomes better. Does this mean the electron is moving around the center of mass, too?

In the helium atom, If the two electrons are not moving to cancel out, the magnetic fields are theoretically produced in almost all areas because the two electrons of the opposite spin magnetic moments are apart by the repulsive Coulomb force.

How can the relativistic effect be explained ? ( The effect of the relativistic mass change by the high speed electron was actually observed.)

 

[Karrar]

I 'm not statisfy

DO you statisfy by this talk ??


if electron move what the force the will push it back to avoid fall in nucleus ??

this force never known at this time

 

[ZapperZ]

Read the FAQ thread in the General Physics forum!

Zz.

 

[Zakk]

Is there a possibility that the electron is colliding into the nucleus all the time
and a new electron is spinning out of the collission ? If this is a continuous process then it also explains why the electron seems to be switching orbits
ZAKK

 

[ZapperZ]

Is there a possibility that the electron is colliding into the nucleus all the time
and a new electron is spinning out of the collission ? If this is a continuous process then it also explains why the electron seems to be switching orbits
ZAKK

Look at the p-orbital geometry. What is the probability that an electron in that orbital actually comes close to the vicinity of the nucleus?

So now you are left with a proposal that is not consistent with our current understanding of the atom. If you wish to propose something like that, you need to come up with a plausible scenario based on what we know and have verified. If not, you will have to propose something quite new, and you will have to do that either in the IR forum, or elsewhere.

Zz.

 

[Zakk]

There are elementary particles that spontaneously decay into less massive particles. An example is the muon, which decays into an electron, a neutrino and an antineutrino, with a mean lifetime of 2.2×10−6 seconds.

This is a known phenomena further Electrons are identical particles because they cannot be distinguished from each other by their intrinsic physical properties. In quantum mechanics, this means that a pair of interacting electrons must be able to swap positions without an observable change to the state of the system.

 

[JayAaroBe]

I've read all the threads relating to this question but my mind is just having trouble with the concept. Let's take the simplest case: a hydrogen atom with one proton and one electron. They have opposite charges and attract. If I think of each as a particle, then my mind wonders why wouldn't the two particles attract each other and come together and collide.

The only way I can make sense of it is as follows, and tell me if this is an okay way to think of it: the electron is not a particle, but rather a spherical cloud of charge. In this case, I think of it the electron not as a single point but rather as the atmosphere around a planet and the planet itself as the proton (I know the sizes are not to scale). This is the only way I can think of it that makes any sense to me and answers the question of why an electron is not pulled into the nucleus (the proton).

 

[QuantumClue]

Since the nucleus of an atom is +charged and the electron is -charged, why doesn't at least one electron fall into the nucleus?

One explanation, I have heard prof. Hawking recite is that an electron cannot settle at the nuclei of atoms because that would give an electron a well-defined position. So the electron does not spiral to the nucleus because it is forbidden by the Uncertainty Principle.

 

[JayAaroBe]

Could you address the bolded part of my post?

I've read all the threads relating to this question but my mind is just having trouble with the concept. Let's take the simplest case: a hydrogen atom with one proton and one electron. They have opposite charges and attract. If I think of each as a particle, then my mind wonders why wouldn't the two particles attract each other and come together and collide.

The only way I can make sense of it is as follows, and tell me if this is an okay way to think of it: the electron is not a particle, but rather a spherical cloud of charge. In this case, I think of it the electron not as a single point but rather as the atmosphere around a planet and the planet itself as the proton (I know the sizes are not to scale). This is the only way I can think of it that makes any sense to me and answers the question of why an electron is not pulled into the nucleus (the proton).

 

[dextercioby]

One explanation, I have heard prof. Hawking recite is that an electron cannot settle at the nuclei of atoms because that would give an electron a well-defined position. So the electron does not spiral to the nucleus because it is forbidden by the Uncertainty Principle.

I think the author of such a statement has a deformed view of the notions involved in the so-called uncertainty principles. He should definitely do more reading.

 

[JayAaroBe]

Could you address the bolded part of my post?

I've read all the threads relating to this question but my mind is just having trouble with the concept. Let's take the simplest case: a hydrogen atom with one proton and one electron. They have opposite charges and attract. If I think of each as a particle, then my mind wonders why wouldn't the two particles attract each other and come together and collide.

The only way I can make sense of it is as follows, and tell me if this is an okay way to think of it: the electron is not a particle, but rather a spherical cloud of charge. In this case, I think of it the electron not as a single point but rather as the atmosphere around a planet and the planet itself as the proton (I know the sizes are not to scale). This is the only way I can think of it that makes any sense to me and answers the question of why an electron is not pulled into the nucleus (the proton).

 

[Chopin]

Could you address the bolded part of my post?

Please do not cross-post--asking your question in one post is sufficient.

You are correct--the electron can be interpreted as a cloud that surrounds the nucleus. The laws of quantum mechanics control how dense the cloud pulls in around the nucleus. Or, if there are multiple nuclei, the cloud will surround them both in a pattern determined by the positioning of the charges. This is the basis for chemical bonds.