quick question

Discussion in 'Physics & Math' started by Asguard, Aug 5, 2008.

  1. Asguard Kiss my dark side Valued Senior Member

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    im trying to round off a question for my chem prac and i wanted to add what held the protons and nutrons in the nuclearous of an atom and what held the electrons to the atom but i cant find the answer anywhere.

    Because this is for a prac it doesnt need to be referenced it just needs to be correct

    Is it the weak nuclear force which holds the protons and nutrons together and then the strong nuclear force which holds the electrons on?
     
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  3. Vkothii Banned Banned

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    Nope. The electromagnetic force keeps electrons bound to protons. The protons in a nucleus bigger than Hydrogen are themselves bound by the strong force.

    The other forces are the weak force which explains neutrons decaying and where electrons "come from", and some other stuff.
    Gravity is the sucker we don't know how to explain, except classically.
     
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  5. Asguard Kiss my dark side Valued Senior Member

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    your sure thats right?
    i dont want to look like a dick
     
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  7. Vkothii Banned Banned

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    Well, no worries if you'd like a second opine.
    I think that's her though.

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  8. James R Just this guy, you know? Staff Member

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    Electrons are negatively charged and protons are positively charged. They are attracted to each other electrostatically. The electrostatic force on the electrons keeps them in orbit around the positively-charged nucleus.

    Why do positive protons, which repel each other, exist together in the very small nucleus? Answer: the strong nuclear force holds them together. The strong force holding them together beats the weaker electric force trying to push them apart.

    The strong and weak nuclear forces have no effect on electrons; they only affect protons and neutrons in ordinary atoms.

    The weak nuclear force has nothing to do with atomic structure, really. It is the force responsible for some types of radioactive decay, though.
     
  9. Asguard Kiss my dark side Valued Senior Member

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    thanks guys, i havent done nulear physics since high school and i was trying to rember off the top of my head

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  10. prometheus viva voce! Registered Senior Member

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    Here's some extra references if you're interested.

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    wiki.answers.com/Q/Why_do_protons_remain_in_the_nucleus
    pubs.acs.org/cen/news/8241/8241notw3.html

    (Sorry I can't link properly to them - I haven't made enough posts yet...)
     
  11. Dinosaur Rational Skeptic Valued Senior Member

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    James R: I think the following is erroneous.
    The above is analogous to saying that the gravitational force prevents planets from faling into the sun.

    There must be some effect which prevents the electrostatic force from pulling the negative electrons into the positive nucleus. The effect would seem to be analogous to the velocity of the planets which prevents gravity from pulling them into the sun.

    The so-called Bohr atom modeled the atom as a small solar system with orbital velocity counteracting the electrostatic attraction. Bohr knew the model was invalid, but realized that it could be used to describe some of the properties of an atom.

    I do not have any idea of what counteracts the electrostatic attraction, but believe that the experts have some reasonable explanation which I might only vaguely understand. I think that the assumption of a classical (Id est: A continuous) orbital path is inconsistent with Quantum Theory & that continuous orbital paths would result in the decay of electron orbits.
     
  12. Vkothii Banned Banned

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    There's the angular momentum both have; there's the exchange of orbital angular momentum with photons, which are coupled to both electric and magnetic moments; a continuous path is only possible if the mass of electrons isn't in any chaotic orbit..

    One or two other things, but that should bring the Bohr model, and Dirac spinors up to date for the now.
     
  13. temur man of no words Registered Senior Member

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    This "effect" is called the centrifugal force. You can explain it perfectly with centrifugal force if you do not take into account Maxwell's theory. It is completely analogous to the planetary system. But by Maxwell's theory accelerating charges must radiate away energy so the electron must fall on the nucleus. This was what Bohr was trying to resolve with his model.
     
  14. Reiku Banned Banned

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    There is a new atomic model that describes the strong force as being the interaction of the casimir force.

    I have a funny feeling this model will be monumental in the years to come. It's about time we had a good picture of the coupling forces of the strong interaction.
     
  15. James R Just this guy, you know? Staff Member

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    Dinosaur:

    No, it's analogous to saying that the gravitational forces is what keeps the planets in orbit, rather than flying off through space in straight lines.

    Yes. It's the same effect - an effect of the tangential velocities of the particles or planets. With planets, the force of gravity from the sun acts at an angle to the velocity direction of the planet at all times - often at close to a right angle. Thus, the force of gravity doesn't change the tangential speed (much) - it just changes the direction of travel of the planet, so that it moves in a circle (ellipse, really) rather than in a straight line.

    In atoms, replace the gravitational force with the electrostatic force, and the (classical) explanation is the same.

    Yes.

    Essentially, the quantum explanation is still the same, only without the well-defined orbits of the Bohr model. The kinetic energy of an electron around an atom (due to its putative speed) counteracts the electrostatic potential energy, resulting in a mean orbital distance. Of course, this is almost a fancy way of saying what I just said regarding forces before.
     

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