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How atoms fuse together

  1. Jan 31, 2013 #1
    Hello, i'd just like to know do atoms fuse together the instant that they make contact after overcomming repulsion or does it take time?

    I've been led to believe that when we touch something we never actually touch it since electrons repel each other and we can't generate enough force to overcome it, so when we touch something it's just the items electric field we are touching/feel and not the actual atoms.

    I guess i'm wondering what would happen if say someone went to clap their hands and just before they did they were zapped by some magic ray which gave them to power to overcome the repulsive force so that the atoms of their hands actually made contact with each other?

    Would they simply just fuse together and have their hands stuck unable to pull apart, would there be a flash of light as energy is released then they are stuck or an explosion instead of just a flash? Would there be an explosion that actually destroys their hands and fused atoms of whatever it is after they fused fall to the ground or get blown away?

    I can picture a dozen things happening if you actually touched other atoms but I have no idea what if any is correct :confused:
     
  2. jcsd
  3. Jan 31, 2013 #2
    Atoms do not fuse together. They make bonds. And they can always come close enough, but will not form bonds unless it is energetically favorable.

    There is no meaning of the word 'touch' in atomic scale just like there is no meaning of the word 'surface' in that scale.

    Your imagined situation sounds so unusual I am not even going to analyse it.
     
  4. Jan 31, 2013 #3

    russ_watters

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    In nuclear fusion, atoms do fuse together.

    You have to overcome both the electromagnetic force and the strong nuclear force (which holds the nucleus together), but yes it is essentially instantaneous.

    It doesn't make sense to talk about it happening to your hands because the energy levels are so high, molecules can't exist...much less hands.
     
  5. Jan 31, 2013 #4
    I believe it is instant. Fusion occurs as a quantum jump.
     
  6. Jan 31, 2013 #5

    Drakkith

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    Consider that fundamental particles are considered to be "point like", meaning they have no physical size. When you feel the force from the atom's electrons, you are truly touching/feeling the "actual atom".

    As I was getting at above, contact at the quantum scale is tricky. There is no real point you could claim that you were touching the atom or not. The force felt from the electrons and the chance to find the electrons in their orbitals simply decreases as you get further away, but it never drops to zero.

    Since you added energy to your hands before clapping, they would probably be moving so fast that when they hit each other they simply disintegrate under the force. There MIGHT be some sort of "explosion" depending on what you mean by explosion. It would be extremely loud and you would be left with no hands either way. And that's a "best case" scenario.
     
  7. Feb 1, 2013 #6
    I believe your hands would just pass one throurgh the other, because at atomic level distances between atoms and molecules are huge. It would be unlikely that even two atoms collide.
     
  8. Feb 1, 2013 #7

    Drakkith

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    This is not true. Atoms are directly bound to one another through molecular bonds. Bonding actually brings them closer together than they would get without bounding thanks to the lower energy state.

    It's important to realize that an atom is a COMPOSITE particle. It is made up of other, more fundamental particles. The electrons surround the nucleus in orbitals that are vaguely analogous to a "cloud" whose density is very high near the nucleus and tapers off as you increase the distance. As two atoms approach each other their "electron clouds" start to repel each other with increasing force the closer the two approach. However, if you can overcome this, and you have the right atoms, the two can bind together and reach a lower energy state. It's kind of like pushing a boulder out of a pit on the side of a hill. Sure you expend some energy getting the boulder out of the shallow pit, but you get much more out of it as it rolls to the bottom of the hill. This is why chemical reactions can release net energy even though they take some to start.

    The distance between the nucleus and the densest part of the electron orbitals is very large compared to the size of the nucleus. Perhaps that is what you were thinking of? This is where the common saying of "an atom is 99% empty space" comes from. (Which is arguable)
     
  9. Feb 2, 2013 #8
    I imagined the situation where we could magically make all forces act normaly between all particles in each hand, but not between the particles of the other hand, except the nuclear forces.
    Then I thought the distances between individual atoms and molecules are huge. You are right about the atom picture, but what about the distance between the molecules?
     
  10. Feb 2, 2013 #9

    Drakkith

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    Why change the way forces work? That doesn't help the OP in their question. But if it were so then you would be correct. It would be a very small minority of nuclei that would actually "collide".

    If they aren't bonded then they can rub right up against each other or be a bazillion light years apart. In your hand all the molecules are pretty close together. It's hard to explain, as it's not just as simple as bonds or no bonds. Cells make up your body and form connective tissue, skin, and everything else. Molecules can wind together without being bonded, interlocking and doing other things that keep your body together.
     
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