Why don't electrons fall into the nucleus?

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Shouldn't the electron fall into the nucleus due to the opposite charges between the two?

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(Original post by AlphaNick)
No.

Air resistance is the net force of air particles (ie oxygen, nitrogen, carbon dioxide, molecules, etc) hitting the object - causing it to slow down.

As Rutherford proved, atoms are almost entirely empty space (excluding the nucleus and the electrons). Therefore, there are no particles on a subatomic scale which exert this force. The space within an atom is essentially a vacuum and is exhausted of particles. So there is no resultant force on the electron.
So what force causes the electron to orbit in the first place then? There must be a 'starting' force to get the electron around the nucleus in the first place and from there, since there is no resistive forces acting on this scale it would continue to accelerate at a constant velocity? What would happen if you removed the proton (say we have a hydrogen nucleus), would the electron just stay at rest?

Also, why doesn't the electron simply fall into the nucleus due to the net positive charge in the nucleus and the negative charge on the electron causing electrostatic attraction between the two?

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Plantagenet Crown
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Because they're electrostatically attracted to the nucleus. Of course though, this is a massive oversimplification and electrons are not really these little particles orbiting a nucleus, it's just easier to imagine them like that.
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(Original post by AlphaNick)
The starting force is simply the electrostatic attraction between the positively charged nucleus and the negatively charged electrons.

If there is no electrostatic force acting on the electron (ie no nearby protons) I would assume the electron continues in a straight line at a constant speed until acted on by a force.

Why they don't fall into the nucleus is a lot more complicated. According to Heisenberg, electrons cannot have a defined location within the nucleus - so it occupies the rest of the space in many different ways. If the electron was specifically certain to be within the nucleus, its momentum becomes exponentially uncertain. Instead they occupy energy levels outside of the nucleus.
Yep, but since the electron is changing direction during it's orbit, the acceleration of the electron is also changing, so shouldn't the direction of the force also be changing so it must have a resultant force to continue acceleration, and so this is caused by the continuous electrostatic attraction.

I know about this and that electrons are in fixed quantum energy states, but doesn't the acceleration of the electron cause it to emit EM waves which should mean it loses energy and decelerates overall?

Also, the probability density for an electron is not non zero within the area of the nucleus, so there is a (very small) probability that it could fall into the nucleus? What would happen in this event? For example, in the n=1 state hydrogen, the most probable position for the electron is at the nucleus itself, so why don't we find it there?

My question is more to do with WHY the electrons are set in specific quantized energy states and quantized energy levels rather than just accepting that they are.

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KongShou
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Electrons do not orbit the electrons. Not in the conventional sense. This is one of the many lies you have been taught at GCSE and A level. Look up the electron cloud and quantum mechanics.

The best explanation to the best of my feeble understanding to your questions are: In an atom there isn't any air to resist the electron, air resistance is caused by air, which is nitrogen oxygen etc. Most of the atom is just empty space. There isn't a starting force to start the electron up, like a motor or something. The electrons are not orbiting, as said above. Particles behave very strangely at subatomic level, which is where quantum mechanics come in. Forget about the classic Newtonian physics, F =/= ma at this level. You cannot directly observe the electrons, as stated by quantum mechanics, and therefore we estimate where each electron is most likely to be at each point in time and "work out" a path for the electrons. The common(only?) ones are the s, p, d, f. It is very similar to calculus where we take the limit of something without working anything out that is specific. I hope this make sense. Quantum mechanics is similar to calculus, at least in my understanding.
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(Original post by KongShou)
Electrons do not orbit the electrons. Not in the conventional sense. This is one of the many lies you have been taught at GCSE and A level. Look up the electron cloud and quantum mechanics.

The best explanation to the best of my feeble understanding to your questions are: In an atom there isn't any air to resist the electron, air resistance is caused by air, which is nitrogen oxygen etc. Most of the atom is just empty space. There isn't a starting force to start the electron up, like a motor or something. The electrons are not orbiting, as said above. Particles behave very strangely at subatomic level, which is where quantum mechanics come in. Forget about the classic Newtonian physics, F =/= ma at this level. You cannot directly observe the electrons, as stated by quantum mechanics, and therefore we estimate where each electron is most likely to be at each point in time and "work out" a path for the electrons. The common(only?) ones are the s, p, d, f. It is very similar to calculus where we take the limit of something without working anything out that is specific. I hope this make sense. Quantum mechanics is similar to calculus, at least in my understanding.
I know about this as well, the electron is treated as a cloud and a probability density function is taken to work out the relative probability of the electron being at any one point.

Could you help with any of the points mentioned in my previous post such as the n=1 probability function of the electron in a hydrogen atom and any of the other questions?

Thanks a lot.

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(Original post by Plantagenet Crown)
Because they're electrostatically attracted to the nucleus. Of course though, this is a massive oversimplification and electrons are not really these little particles orbiting a nucleus, it's just easier to imagine them like that.
Yep, I know this, perhaps my question was a bit badly phrased.

Could you please help with any of the questions in my post below yours?

Thanks a lot!

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(Original post by majmuh24)
Yep, but since the electron is changing direction during it's orbit, the acceleration of the electron is also changing, so shouldn't the direction of the force also be changing so it must have a resultant force to continue acceleration, and so this is caused by the continuous electrostatic attraction.

I know about this and that electrons are in fixed quantum energy states, but doesn't the acceleration of the electron cause it to emit EM waves which should mean it loses energy and decelerates overall?

Also, the probability density for an electron is not non zero within the area of the nucleus, so there is a (very small) probability that it could fall into the nucleus? What would happen in this event? For example, in the n=1 state hydrogen, the most probable position for the electron is at the nucleus itself, so why don't we find it there?

My question is more to do with WHY the electrons are set in specific quantized energy states and quantized energy levels rather than just accepting that they are.

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Even though I do think it's possible to force electrons into the nucleus, it doesn't naturally happen because of the ground state energy i.e. the electron must always have a minimal energy which it will not further give up.
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Well one of the main reasons why the nucleus does not collide is due to the strong nuclear force.
At certain distances it attracts and brings things closer but when it's too close it starts to repel hence no collision occurs.
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uberteknik
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(Original post by majmuh24)
So what force causes the electron to orbit in the first place then? There must be a 'starting' force to get the electron around the nucleus in the first place and from there, since there is no resistive forces acting on this scale it would continue to accelerate at a constant velocity? What would happen if you removed the proton (say we have a hydrogen nucleus), would the electron just stay at rest?

Also, why doesn't the electron simply fall into the nucleus due to the net positive charge in the nucleus and the negative charge on the electron causing electrostatic attraction between the two?

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The orbiting electron analogy evolved into the more accurate Bohr-Rutherford model, but even this model falls apart exactly because it does not predict the behaviour of the atom for the reasons you have identified.

In other words it's simply wrong and no planetary-orbital model can predict the behaviour of the electron.

To get a better model one has to embrace quantum mechanics (which was developed to answer this paradox) and at a simple level of abstraction, you have to completely disregard the idea that electrons have a defined trajectory.

It's also more appropriate to think of the electron not as a particle but as a wave and a representation of energy.

In quantum mechanics, electrons are defined as having discreet energy levels constraining the space they are allowed to occupy around the nucleus. It also predicts that electrons cannot occupy the same space as the proton. Quantum theory is wierd in the extreme and the classical definition of causality for every event does not apply.

In essence, when you get down to physics at the sub-atomic level the 'why' question cannot be answered because it's the limit of physics knowledge.

The mathematics describes the observations of the atoms behaviour to a high degree of precision. But it does not explain why they happen.

Richard Feynman quotation:

"What keeps the electrons from simply falling in? The uncertainty principle: If they were in the nucleus, we would know their position precisely, which would require them to have a very large, but uncertain, momentum, i.e., a very large kinetic energy. This would cause them to break away from the nucleus. They make a compromise: they leave themselves a little room for this uncertainty and then jiggle with a certain amount of minimum motion in accordance with this rule."

Still a lot more Nobel prizes to be had if you can get closer to the answer!
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(Original post by uberteknik)
The orbiting electron analogy evolved into the more accurate Bohr-Rutherford model, but even this model falls apart exactly because it does not predict the behaviour of the atom for the reasons you have identified.

In other words it's simply wrong and no planetary-orbital model can predict the behaviour of the electron.

To get a better model one has to embrace quantum mechanics (which was developed to answer this paradox) and at a simple level of abstraction, you have to completely disregard the idea that electrons have a defined trajectory.

It's also more appropriate to think of the electron not as a particle but as a wave and a representation of energy.

In quantum mechanics, electrons are defined as having discreet energy levels constraining the space they are allowed to occupy around the nucleus. It also predicts that electrons cannot occupy the same space as the proton. Quantum theory is wierd in the extreme and the classical definition of causality for every event does not apply.

In essence, when you get down to physics at the sub-atomic level the 'why' question cannot be answered because it's the limit of physics knowledge.

The mathematics describes the observations of the atoms behaviour to a high degree of precision. But it does not explain why they happen.

Richard Feynman quotation:

"What keeps the electrons from simply falling in? The uncertainty principle: If they were in the nucleus, we would know their position precisely, which would require them to have a very large, but uncertain, momentum, i.e., a very large kinetic energy. This would cause them to break away from the nucleus. They make a compromise: they leave themselves a little room for this uncertainty and then jiggle with a certain amount of minimum motion in accordance with this rule."

Still a lot more Nobel prizes to be had if you can get closer to the answer!
Repped, you've cleared up a lot of stuff for me, but there's still a few questions I have left.

Can't the question be 'explained' by thinking of the electron as a solid little particle with an*accompanying wave which pushes it around (i.e. wave-particle duality => two things rather than one, which is the viewpoint of the de Broglie-Bohm theory, whereas QM is just a dynamical theory and more to do with the statistical mechanics of particles moving along non-classical paths?

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(Original post by majmuh24)
Shouldn't air resistance when orbiting should cause them to decelerate and eventually stop orbiting or even fall into the nucleus due to the opposite charges between the two?

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Why are we turning simple chemistry into very complicated physics??? My head hurts....
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(Original post by Nissie1)
Why are we turning simple chemistry into very complicated physics??? My head hurts....
It's not that simple. Simple chemistry tells you that opposite charges attract, but it also tells you that the electron has a negative charge and the nucleus has a net positive charge. Simple chemistry doesn't explain why the small electron doesn't just fall into the much larger nucleus.

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(Original post by majmuh24)
It's not that simple. Simple chemistry tells you that opposite charges attract, but it also tells you that the electron has a negative charge and the nucleus has a net positive charge. Simple chemistry doesn't explain why the small electron doesn't just fall into the much larger nucleus.

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All chemistry is kind of simple....
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(Original post by Nissie1)
All chemistry is kind of simple....
Not sure if trolling
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zed963
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(Original post by Nissie1)
All chemistry is kind of simple....
No it's not, a lot of the electron and sub levels go into QM. The electron excitation is explained by this. Even hybrid orbitals are explained.

There's a lot more to learn yet. It's all at degree level.
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(Original post by n00bfi)
Not sure if trolling
I'm being sop serious... I just don't get physics, it makes no sense but chemistry is beautiful....
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(Original post by zed963)
No it's not, a lot of the electron and sub levels go into QM. The electron excitation is explained by this. Even hybrid orbitals are explained.

There's a lot more to learn yet. It's all at degree level.
I don't mind having to learn all that because I love chemistry so no matter how hard it gets I'll still love it
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(Original post by Nissie1)
I don't mind having to learn all that because I love chemistry so no matter how hard it gets I'll still love it
Okay then.... Maybe when you get to that level you'll realise that even the most brilliant of scientists haven't cracked the fundamentals.
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(Original post by Nissie1)
All chemistry is kind of simple....
What is the concentration of Ag+ in a solution if it takes 2.30 mins using a current of 2.00A to plate all the silver from 0.25L of a solution containing Ag+?

Work out the answer to that and then get back to me on chemistry being simple. :rolleyes:
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