The Atom

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The Atom
« on: July 01, 2006, 06:19:55 PM »
I was reading a book which talked about the four forces in the universe (gravitational, electromagnetic, strong-nuclear, and weak-nuclear) and I came up with a question.  An electron orbiting around the nucleus of an atom is being pulled towards the nucleus with the gravitational force.  The electromagnetic force is much stronger than the gravitational force, and it too is pulling the electron towards the nucleus.  So my question is:  why do the electrons still orbit and not just get sucked in by the (strong) electromagnetic force added to the gravitational force?

Note:  My friend provided a possible answer to this question that I won't post right now.  I'm curious to see if anybody else thinks of the same thing.
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cadmium_blimp

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The Atom
« Reply #1 on: July 01, 2006, 07:49:50 PM »
I don't know about the electromagnetic force, but I think gravitational force is dependant on the mass of both objects.  If a person goes into orbit around earth and goes on a spacewalk and loses a wrench in the process, it won't go flying towards the earth even though the earth is huge and should have a large amount of gravitational pull and the wrench shouldn't be able to resist it.  They have to work together.  Assuming RE physics are correct, I could still be all wrong.

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Erasmus

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The Atom
« Reply #2 on: July 02, 2006, 09:55:34 AM »
Quote from: "cadmium_blimp"
I don't know about the electromagnetic force, but I think gravitational force is dependant on the mass of both objects.


That's true.  It's also true that the electromagnetic force is dependent upon the charge of both objects, in a similar way to the way that gravity is dependent on the masses (in a sense, mass is a "gravitational" charge).

One way to resolve your confusion is to think of orbits.  Satellites orbit the Earth, planets orbit the sun, etc., despite the attractive forces between them.  This is just because the satellites/planets are moving.  They're constantly falling towards the Earth/sun, but they're moving in a perpendicular direction at the same time, so they never quite reach the ground.  Electrons move very quickly in their orbits, and the speeds are just enough to keep them from falling into the nucleus.

Another, better way to think about it is to abandon the notion of electrons moving in circular orbits around the nucleus and adopt the quantum theoretic notion of orbitals and wave functions.  The orbitals, instead of being regions that the electrons travel through, define the probability that an electron will be found in a given location.  These probabilities take into account the electromagnetic attracion between electrons and protons.
Why did the chicken cross the Möbius strip?

Re: The Atom
« Reply #3 on: July 02, 2006, 11:50:04 AM »
Quote from: "Knight"
I was reading a book which talked about the four forces in the universe (gravitational, electromagnetic, strong-nuclear, and weak-nuclear) and I came up with a question.  An electron orbiting around the nucleus of an atom is being pulled towards the nucleus with the gravitational force.  The electromagnetic force is much stronger than the gravitational force, and it too is pulling the electron towards the nucleus.  So my question is:  why do the electrons still orbit and not just get sucked in by the (strong) electromagnetic force added to the gravitational force?

Note:  My friend provided a possible answer to this question that I won't post right now.  I'm curious to see if anybody else thinks of the same thing.


On the microscopic level, the gravitational force is vitually null. the electromagnetic force is more then 100000000 times stronger then it. And as erasmus stated, electrons exist only in a quantum state until measured. So you need to stop thinking of electrons and other particles as tiny bits of matter all of the time. This means they are basically a wave of potentials around the nucleus. This wave has peaks and troughs like any other wave. On certain orbits around the nucleus, the peaks and troughs of the waves will coincide with each other, giving us the allowed orbits.

The Atom
« Reply #4 on: July 02, 2006, 11:54:56 AM »
Quote from: "cadmium_blimp"
I don't know about the electromagnetic force, but I think gravitational force is dependant on the mass of both objects.  If a person goes into orbit around earth and goes on a spacewalk and loses a wrench in the process, it won't go flying towards the earth even though the earth is huge and should have a large amount of gravitational pull and the wrench shouldn't be able to resist it.  They have to work together.  Assuming RE physics are correct, I could still be all wrong.


The wrench with eventually fall out of orbit. Meaning that it's transversal velocity against the earth will be sufficently reduced so that it's trajectory will be changed and slowly curve into the earth and not around it. To orbit something is to fall into it's gravity but keep sufficent transversal velocity to "miss" the object each time so you keep going around it.

The Atom
« Reply #5 on: July 03, 2006, 05:34:27 AM »
The reason that electrons aren't all in the nucleus with the protons, why they stay in orbitals, is due to there own repulsion. if you consdier hydrogen, the electrons are very close to the nucleus, however the more electrons that you add the greater and greater the repulsion becomes and the more they repulse each other. There is aslo Pauli's exclusion principle that states that no two particles with half integer spin may have the same quantum numbers (ie they have to be in diffrent orbitals or have opposite spin - electrons have 1/2 or -1/2 spin).


Also due to Heisenbergs uncertainly principle, even though the electron may preferentially be next to the nucleus, it won't always be.

The Atom
« Reply #6 on: July 03, 2006, 06:55:59 AM »
Quote from: "DrQuak"
The reason that electrons aren't all in the nucleus with the protons, why they stay in orbitals, is due to there own repulsion


If you have two atoms next to each other, the electrons of each atom repulse each other--but at the same time, they are being pulled towards their own nucleus.

I suppose part of the reason electrons are in orbit is that they are attracted to the nucleus of every atom surrounding it (thus, pulling it away from its own nucleus--even though the electrons are pushing it away).
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Erasmus

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The Atom
« Reply #7 on: July 03, 2006, 09:08:10 AM »
Quote from: "DrQuak"
The reason that electrons aren't all in the nucleus with the protons, why they stay in orbitals, is due to there own repulsion.


Not all atoms have more than one electron.  Even if you consider a single hydrogen atom in otherwise-empty space, the theory still predicts the orbital model of the atom.
Why did the chicken cross the Möbius strip?