Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Solid mater?

  1. Feb 9, 2009 #1
    some one told me that if a nucleus is the size of a marble
    and the electron is the size of a bb
    that the distance between them is like 2 MILES!
    is this true ?
    if so how can matter be so... solid?
  2. jcsd
  3. Feb 15, 2009 #2
    Just to jump start this a little, recall that flowing water is not considered a solid, but frozen water is, yet frozen water is less dense!
    Granted, that's a special circumstance but it illustrates that "solidity" is not wholly dependent on "density"

    When atoms form molecules, and those molecules bind covalently with each other in such a way as to make that whole structure "rigid", or non-moving with respect to each molecule with another, we can consider that object to be solid.

    That spacial rigidity might be relatively fragile(ice cube, or sheet of common glass) or very strong(diamond), but they are all considered solids.

    Anyway, this subject is vast. Perhaps a Wiki treatment on the states of matter might help more than I can.
  4. Mar 8, 2009 #3
    First the electron would still be too small to see no matter how much you enlarge. But this doesn't matter. The electron forms a density cloud, basically all the electrons do that. These clouds repel, and since everything is made of them nobody notices that the electron is so small. This can only be seen, if you use something very small to probe where the electron is, (for example a very fast electron, that is not bound to a nucleus does the job)

    Another way of getting a feel for it is with magnets. If you have two magnets on a rail that repel each other and you are pushing one of them with a magnet, then the other one will be pushed too. Now imagine solids are big 3d grids of nuclei with forces that try to keep them always at the same distance (due to the electron density clouds). If you have another grid like that colliding with the first they behave like solid objects, even though its just large numbers of little nuclei that try not to get to close.

    All of this is of course full of inaccuracies, for the real picture you need electrodynamics and quantum mechanics.
  5. Mar 8, 2009 #4
    this is more on what i was asking rather then states of mater ...
    that they all repel like magnets makes for easier understanding
    thanks had not considered charges
    there was some thing i heard of all the "empty" space in an atom that i did not under stand why it was so 'solid' - not as in that even hydrogen can be a solid material
  6. Mar 8, 2009 #5
    My physics class had a hard time getting used to that idea. :)
  7. Mar 9, 2009 #6
    now on the thought of comparing magnets and electrical charges >>>
    it is possible to have a negative charge with out a positive as in the fast electron
    is it also possible to have a positive or negative magnetic charge with out the other?
    as in a mono-pole magnets that only have a North or South field?
  8. Mar 10, 2009 #7
  9. Mar 10, 2009 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    This is now a completely different topic than your original post. This may be a strange advice, but do not hijack your own thread. I presume that with this question, your original question has been answered. So please start another thread in the Classical Physics section that is more appropriate for your new question.

  10. Mar 10, 2009 #9


    User Avatar

    Staff: Mentor

    I'll just add that there's a very practical reason to your benefit why you should start a new thread when you change the subject completely. In this case, for example, you're much more likely to attract responses from people who actually know something about the status of magnetic monopoles if you start a thread with a name like "Do magnetic charges exist?" than if you bury it inside an ongoing thread with a name like "Solid matter?" Most people don't read every single thread in a forum, but instead pick and choose based on the names.
  11. Mar 10, 2009 #10
    thank you !
    i will ... a knife forum were i go a lot this happens all the time ..
    it really is a good idea as you said if it is knowledge you are seaking!
  12. Mar 12, 2009 #11
    In hard materials, like a crystal, the electrons need to be considered as a wave, as some people express as cloud, so electrons are spread around the nucleus as a result forming a electron shield around the solid matter. Now when you hit it with other solid to test solidity, the other solid also has a shield outside. So during touch 2 electron shields will confront and will repel each other, because quantum mechanical principle does not allow electrons mixed easily in terms of allowable state.
    So, the analogy in the post#1 is not a good one in modern quantum physics picture. Better one is electron is similar to a cloud surrounding the nucleus in solid state material case.
    Last edited: Mar 13, 2009
  13. Mar 13, 2009 #12
    yes i looked up that and cloud is good description
    they said cloud is the

    'probability of location of an electron at any one moment of time"

    that it most likely not in a circular orbit but that 'floating' around could be a way to describe it..

    my question was from were i seen some thing saying of how much space a atom took
    in that if the nucleus was the size of a golf ball that a proton/nutron was the size of a small BB
    and that the electrons would be a speck about 5 miles away! which seems a lot of space !!!
    yet i know that electrons 'flow' in conductors and that current in a wire has a skin effect due to the like charges
    which is why HV stations use pipe not sold bars for current distribution ..
    i did not quite understand how powerful a charge the electron has..
    that it would span that much 'space' on a atomic scale..
  14. Mar 13, 2009 #13


    User Avatar
    Science Advisor

    Well, the problem with theose, analogies, as pointed out, is that 'size' doesn't matter.

    The volume of an atom's nucleus could be 1/10 the size, or 1/100 the size, or even an infinitely small dot - and it would not change your everyday world one bit. Because the volume of the nucleus just don't really matter at all to the electrons. The charge is what matters (and to a much smaller extent, the mass, and the weird property known as 'spin'). In fact, atomic and molecular physicists routinely work with models just like that - with the atomic nucleus as an infinitely small point.

    So for all intents, the size of an atom is dictated by where the electrons that encircle it hang out. But they don't 'orbit' the nucleus like planets. They don't stay at any particular distance. Sometimes they're very close, sometimes they're very far away. But their average distance is indeed huge in comparison to the size of the nucleus. But electrons don't really care about that :-) And the space is not quite 'empty'.

    But the charges aren't what causes the 'size'. The opposite charges of the electron and nucleus attract, so it 'wants' to be close to the nucleus. But it gains energy doing so - kinetic energy. The closer an electron is to the nucleus, the faster it moves (and in this way, it is like a planet). This motion takes it away from the nucleus. So where all these things balance out is where the electron is most likely to be. The 'main' reason it's so 'big' is that electrons are pretty light, especially compared to the nucleus. If they weighed a lot more, they wouldn't speed up so much, and could get closer to the nucleus.
  15. Mar 13, 2009 #14
    this gets more informative all the time!
    yes some of what i read did mention spin and also flavor,
    charm and up and down ????...
    that these words are not descriptive but rather used to denote some
    detectable property but one that defies defining..

    i did not know that he nucleus was so small .. as i said what i seen..
    [[and i hate to admit it was on TV]]
    was about how much space was in an atom and that in that light
    how it was NOT as solid as we thought
    i asked here as this place is not full of those wanting to be on tv..
    ie the real world..

    and now that you say it is not empty space in side of the orbit of the electrons
    what is in there ? strings?

    gee now i wander of anti-mater..
    is it to be expected that it also has some of the same properties?
    and how will it really react on exposure to normal mater?
    i don't believe we can get warp out of it.. but what?

    i lived in Tx when they aborted the big ring tunnel jest south of dallas..
    this would have gave more info? or black holes like the euro one?
  16. Mar 13, 2009 #15
    One thing I know of anti-matter is that positron is used actually in medical application to detect abnormal cells in human. Some substance is taken to the patient and the material gathers high concentration at certain abnormal cells. Now the positron is released from that substance then it travels quite short distance to react with electron, as a result they were converted to gamma rays. By detecting these rays we can pin point the prob cells.
  17. Mar 13, 2009 #16
    AH ha! is this what they call a pet test?
    my wife had has them during her cancer fight..
  18. Mar 14, 2009 #17
    The positron tool should be similar to the pet tool which uses a lot of x-rays and frequent use is not desirable. Well, many tools have some hazard actually.
  19. Mar 17, 2009 #18
    I was wrong sorry. The pet scan is correct for positron tool.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook