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Particle Size VS Atom Size

  1. Jun 22, 2006 #1


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    I have a question about atom size VS particle size. The size of an electron, proton, and neutron (or really how much space they occupy) as compared to the amount of space they take up when they are assembled as an atom. I read somewhere that the particles are actually like millions of times smaller that the volume occupied when they are part of an atom. The electron is orbiting very far from the nucleus and all of the particles are much smaller that the volume of a functioning atom. Has anyone figured out exactly how much the increase in volume actually is?
    I once heard someone say that if you could bring Lake Superior down to absolute zero, it would disappear before your eyes. The space occupied by the unbound atomic particles would be millions of times less than when the particles were part of functioning atoms. All of the mass would still be there but you couldn’t see it. Is this true?
  2. jcsd
  3. Jun 22, 2006 #2


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    You're sort of right. Atoms are indeed mostly empty space. You will not, however, shrink them by cooling. Atoms don't know from temperature; that's a molecular function. Shrinkage occurs through the application of extreme force, such as gravity in a neutron star or impact in an accelerator. The most compact atom that you can get is in actuality a neutron, unless there's some stage between that and a black hole, of which I've heard some mention. Neutronium, also called degenerate matter, is formed when the electrons are actually crushed into the protons to form neutrons. The density is about what you'd get if you compacted a dozen cars into the size of a teabag.
    This is not an area of expertise for me, so others will have to explain further.
  4. Jun 22, 2006 #3


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    I thought that in the absence of heat (absolute zero) that the atoms just "turned off", that the elctrons stopped orbiting and all of the particles were now free to just "wander" and did not feel each others presence. Wrong?
  5. Jun 22, 2006 #4
    Yep. But it sure gets kinda weird:


    Ultracold plasmas and Rydberg gases
    Exotic, ultracold states of matter are challenging physicists to draw on expertise from atomic, condensed-matter and plasma physics, and causing a few surprises along the way. The ultracold world has fascinated and surprised scientists since 1911, when Heike Kamerlingh Onnes discovered superconductivity in mercury at 4.2 K. Now physicists routinely achieve temperatures millions of times colder. When atoms are cooled this close to absolute zero, they fall into the lowest possible quantum state with bizarre consequences...
  6. Jun 22, 2006 #5

    Claude Bile

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    The diameter of atomic nucleii typically measure in the ballpark of femtometres (1 fm = 10^-15 m), whereas the diameter of atoms measure around tens of picometres, up to about 100 pm for large atoms (1 pm = 10^-12 m).

    Volume-wise, atomic nucleii are roughly 15 orders of magnitude smaller than the atom itself.

  7. Jul 12, 2008 #6
    i read somewhere once that if all the space was removed from the earth and just matter was left it would be approximately that of a matchbox. is this true. can anyone give an accurate size of the earth should it only consist of matter without space. please please someone give me a correct answer.
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