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What FORCE hold metals together?

  1. Jul 20, 2005 #1
    I feel like this is something I should already know, but I don’t even know what to search for to find an explanation.

    Solid pure metals like piece of Iron, Copper, or Nickel are made up of atoms all the same (Cu, Fe, or Ni). Each atom has a positive nucleus surrounded by a field of electrons. So at very close proximity the shell of electrons should serve to keep the atoms apart for the others. BUT what holds them to make the metal? What “force” holds the atoms tight together to make the metal as we see it.??

    Couldn’t be gravity – much to weak at these levels.
    Not the Strong force – that’s for inside the nucleus
    Weak force – NO to weak and serves to overcome the strong in breaking a nucleus.
    That leaves Electric or Magnetic.

    Unless there’s another force I don’t know about it must be EM.
    The same EM that keeps the atoms from getting to close to each other and repels the floor away from the bottom of my shoes forcefully enough to keep my weight from sinking into the floor.
    So EM must also be doing something to keep the atoms together, tight enough to make the metal. HOW?

    Is there a name for what’s going on so I can find a site that discusses or explains it?

    (I bet it’s simple)
    Thanks RB
     
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  3. Jul 20, 2005 #2

    ZapperZ

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  4. Jul 20, 2005 #3

    Gokul43201

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    RandallB, why is your amazement only restricted to metal atoms ? Are you not amazed that there must also be an electrostatic force that holds together carbon atoms in a piece of diamond ? In fact, you should, for the same reason, be amazed that a molecule can even form. The reason for all these happenings stems from a single common idea, which is the following :

    If I take two objects which are essentially composed of a poinlike, positive center surrounded by a uniform, negative cloud (or vice versa), then the force between these identical objects is repulsive up to a certain distance and attractive beyond that distance. So, these objects end up in equilibrium, at this specific distance where the force between them vanishes. This is also, as a consequence, the distance at which the energy of interaction is a minimum.

    This one underlying principle unifies the reasons why (i) molecules form, (ii) metals are hard, solid objects, (iii) you don't fall through the floor.

    The details, however, vary from one kind of material to another. I'm not too fond of the explanation provided by Zz's link. I recommend that you start here :

    http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html

    ...and then go here ...

    http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/bond.html

    ...and finally, here ...

    http://www.chemguide.co.uk/atoms/bonding/metallic.html
     
  5. Jul 21, 2005 #4
    Bonding (both ionic and covalent) provides a description of the amazing ability of solids to hold themselves together. Even the rule that atoms need to try to be surrounded by a complete shell of electrons is just a part of the description that works well for chemistry.

    But I’d like to understand and explain the “force” that makes this work.
    Closest to that is:
    This principle is the force explanation I’m looking for.
    And it seems to me based less on the EM force as a whole and more on the Electrostatic Force half of the EM force. And a bit of geometry to explain how the Electrostatic Force is acting on a pair of identical atoms to both attract and repel.
    Understanding how this "force" works it seems to me is fundamental to accepting the “Amazing” rules and descriptions of bonding.

    Does this “force” have a name?
    Anybody know of a good site that focuses on the interaction of these attraction and repulsion forces between identical atoms.

    RB
     
  6. Jul 21, 2005 #5

    Gokul43201

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    An EM interaction can be purely electrostatic, purely magnetostatic or a mixture of both. And you can switch from one to another, simply by changing your frame of boservation.

    The "force" that you want to name is exactly what you previously called it - it is nothing but a simple electrostatic force. In fact, it is merely the vector sum of 4 different elemental electrostatic forces :
    (i) repulsive force between nucleus(A) and nucleus(B)
    (ii) repulsive force between electrons(A) and electrons(B)
    (i) attractive force between nucleus(A) and electrons(B)
    (i) attractive force between electrons(A) and nucleus(B)

    What is non-trivial to show is that these forces do not simply cancel each other off (except at a particular - the equilibrium - internuclear separation).
     
  7. Jul 21, 2005 #6
    Now we are in the same show.
    Of the four electrostatic forces :
    (a) repulsive between nucleus(A) and nucleus(B)
    (b) repulsive between electrons(A) and electrons(B)
    (c) attractive between nucleus(A) and electrons(B)
    (d) attractive between electrons(A) and nucleus(B)
    All are inversely proportional to the distance between them and all go towards zero at any significant distance.
    Force “a” is likely the simplest to describe as a function of distance squared.
    The other three look like the geometry of function that describes them must be a bit more complex.
    “c” & “d” have to be much stronger at distances, and although b likely important, I guessing that “a” is most significant a very close distances.

    Assuming we are dealing with identical atoms with point source nucleus inside a even distribution electron cloud. This would lead to the most straightforward explanation to detail but still complicated I’d guess.

    It’s this “discovery” or first to document this explanation how these four forces work to hold solids together that I expected would have a name of some kind or for somebody. Seems rather fundamental and important to how our world works, someone deserves some credit for it. And I assume it also accounts for how liquids are held together (just not as solidly – pun) from dispersing into a gas.

    Do you know of any sites that goes into the details of this non-trivial explanation and maybe goes into some of the issues that must impact on it with non uniform electron clouds and non point like nucleus as must occur using molecules.

    thanks
    RB
     
  8. Jul 22, 2005 #7
    Why couldn't you model molecules with pointlike nuclei? It's the electrons that count in binding the atoms to eachother.
     
  9. Jul 24, 2005 #8

    Astronuc

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    The states of matter were understood for more than 2000 years before the fundamentals were discovered.

    I don't believe there is a particular site addressing what you have in mind. Gokul and ZapperZ have already given links to sites that discuss atomic bonding.

    What you are thinking of is basic atomic physics and more elaborately quantum mechanics. The field of QM has numerous contributors whose names have been applied to specific phenomenon. Remember names like Planck, Bohr, Heisenberg, etc.
     
  10. Jul 24, 2005 #9

    Gokul43201

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    I used that picture as a very simplistic means of communicating the nature of the force between atoms and to raise the important point that in equilibrium, THERE IS NO FORCE.

    The realization that electrostatic forces bind atoms was hardly a realization. In fact, these mechanisms were proposed long before the structure of the atom (Rutherford) was even reasonably known.

    In fact, the bonding process is hardly this simple. And Quantum Mechanical models (molecular orbitals, tight binding models, etc.) rarely use forces to explain interactions.
     
  11. Jul 24, 2005 #10
    What are you talking about? What does hold a solid together then, Magic?
    Of course there is a force, just because there’s “equilibrium” doesn’t mean no force is involved.
    If a solid was to change towards a higher density – the force would move the atoms back to ‘normal’ if the movement was towards less density like a liquid or even separating the atoms into a gas, without added energy to overcome “The force” this force would return or hold the solid in equilibrium.

    It took me awhile but I finally found an appropriate name for the force:
    “INTERATOMIC FORCE”
    , pretty straight forward name I guess.

    That’s a neat trick, I like to see a version that explained the mechanisms of:
    (a) repulsive between nucleus(A) and nucleus(B)
    (b) repulsive between electrons(A) and electrons(B)
    (c) attractive between nucleus(A) and electrons(B)
    (d) attractive between electrons(A) and nucleus(B)
    Without the knowledge of Rutherford’s atom.

    Anyway
    Sure is right. Yesterday I was able to get my hands on a book by Mike Finnis © 2003 Oxford Press, Titled “interatomic forces in condensed matter”
    and for info like this 2003 is like being printed yesterday.
    And this was able to ‘amaze’ me.
    Before, you can even begin to review an interatomic force model, he includes about 60 pages of “Essential QM” plus another 60 on some additional Theories and Principles.
    That is, although at first look, the electrostatic forces involved you might think it is a 3 dimensional geometry problem with a rather complex “Classical” description. BUT, The useful Descriptions currently are dependent upon the uncertainty principal within QM.
    That surprised me, that a more classical explaination does not seem to have been attempted.
    RB
     
  12. Jul 24, 2005 #11

    Gokul43201

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    Don't have much time now, so I'll just say one little thing.

    It doesn't take a force to maintain equilibrium; it takes a force to change things.

    When a solid is in equilibrium (nodoby is stretching or twisting the solid) there is no net force on the atoms. It doesn't take magic for things to not change in the absense of a net force.
     
  13. Jul 25, 2005 #12

    Chronos

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    Binding of atoms is very simple. Adjacent atoms share outer electron shells.
     
  14. Jul 25, 2005 #13

    ZapperZ

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    Unless I missed something, the original question here is about METALS, no? So this is not just any old generic "two atoms coming together" type scenario.

    I think I've tried to point to a site (that Gokul didn't like that much), and Gokul had also pointed to several other sites that dealt with what is know as "metallic bonds". Keep in mind that the valence electrons are NOT LOCALIZED in a metal. The bonds are form with a slightly different mechanism.

    And regarding this "there must be force" thing, this is getting utterly silly. First of all, QM doesn't deal with "force" even though one can, if one wants to, "derive" this force. One NEVER deals with any force when dealing with bound states. It doesn't mean there is no force, it just means WHY would one wants to deal with that when everything that we need to describe the system are already available with resorting to such tedious calculation! Again, look at the situation in classical mechanics when dealing with the Lagrangian/Hamiltonian mechanics - there is NO EXPLICIT FORCE involved in that formulation either!

    I think a review of a standard Solid State text is in order here.

    Zz.
     
  15. Jul 25, 2005 #14
    Come on -- even in your land of OZ you must see there is a difference between “THERE IS NO FORCE” and no NET force. Or is my not falling through to the floors below me because “THERE IS NO FORCE” rather than NET of the real force of gravity holding me down and the real force from the floor holding me up.
    And we don’t need “nodoby” to stretch or twist the solid; the temperature and motion of the individual atoms on their own to disfigure the solid is real enough, but checked by the “intra-atomic” forces we are discussing, holding the solid in place as a solid.

    As to starting this thread off talking about ‘metals’ – obviously that was because I didn’t know the force I was trying to talk about. Just did the best I could to describe it in order to find it. Worked well, your description was on point so that I could find the term “interatomic force” that lead me to the book I listed.

    Also note: I lose the bet I made in the first post that the answer would be simple. I agree with your point that a trivial explanation like sharing electron’s in the outer shell is a significant oversimplification. Just a light review of the Mike Finnis book will confirm your point on that.

    As to QM explanations not recognizing forces in their descriptions. I’ll put that off on QM’s ability to use uncertainty. While I’m trying to look at look at things from a classical view, or as Louis De Broglie would have put it a more Cartesian approach in a return to spatiotemporal descriptions. I don’t have the math skill to do so in the intra atomic area and I find it unfortunate that those that do are already to busy using QM.

    RB
     
  16. Jul 25, 2005 #15

    Gokul43201

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    We're digressing a little bit here, but nevertheless, a rigid body with no net force on it (despite having several forces acting on it) translates exactly as a body with no force on it does (we know this thanks to Newton). There is no difference between the two scenarios, with respect to this single body. If there was no floor below you and no gravity too, you'd stand exactly in the same place as you are now.

    Very true. What I was trying to highlight is the fact that "at the equilibrium spacing, there is no force between the atoms. However, when slightly discplaced from this equilibrium, there is a restoring force (like in a spring). Temperature causes these small discplacements. But even in the absence of such microscopic motion (hypothetically) a solid would remain "solid" despite the force between atoms being equal to zero. Sollidity is a feature of the interactomic spacing and the response of the material to applied forces. Also, while I say the interatomic force is zero, in equilibrium, this certainly does not mean that the interatomic (electrostatic potential) energy is zero.
     
  17. Jul 25, 2005 #16

    ZapperZ

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    If you think you can use "classical description" to describe the physics of solids, you're more than welcome to show how you would come up with the band structure of the semiconductor that you are so using in your electronics. You're dissing something, the fruits of which you are using ignorantly. And the fact that you do not even understand basic solid state physics but you are not hesitant to make such statements shows to me, at least, that you don't care to learn.

    If you care so much about classical view, study Lagrangian/Hamiltonian mechanics and convince yourself the concept of "force" is often unnecessary, EVEN in classical mechanics. Period!

    Zz.
     
  18. Jul 25, 2005 #17
    I think I was clear on that point as I already said "I don’t have the math skill to do so .. " but I have a real sence that those that do, if they would by getting clear of the QM dogma (Ref: L. de Broglie) some really amazing stuff could be uncovered.

    As to using the classical method, be patient, I’ll get there, I’ve only been at this since last October.

    Even if there is a technique that I can ignore forces by. I prefer to recognize that I’m not in space, that there is a floor holding me up in a gravity field and account for the forces involved, even if they do NET out. Just because you can doesn’t mean you have to.

    And No Gokul I don’t think we’ve digressed here at all, I may have miss-named the Thread out of ignorance, but you guys have got me to exactly the information and resources I needed. How better to find my way to knowledge.
    Thanks guys.

    RB
     
  19. Jul 25, 2005 #18
    What exactly is the QM dogma? Considering that semiconductors can not be explained via classical theory I doubt that losing any dogmas can produce anything interesting.
     
  20. Jul 25, 2005 #19

    ZapperZ

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    However, ignorance is not a valid excuse to counter-attack the stuff you do NOT understand! You are arrogant in insisting that YOU have a better approach to this DISPITE the fact that the GREATEST success of QM is in this very field you are trying to deal with - solid state/condensed matter physics. You have the SMALLEST glimpse of the whole field, but that somehow doesn't stop you in making all these outrageous statement.

    It leads me to believe that your original question is utterly insincere. You asked about bonding in metals. When you were given the established answers, you DISPUTED that and insisted that YOU have a "classical" answer. When you are confronted with proving that you have actually understood the standard treatment of solids, you produce the convenient excuse that you "don't have the math". Yet, you claim to know something better? What kind of a hoax do you think you're pulling here?

    This thread has produced ZERO progress. It appears to be a very sneaky avenue for you to push some crackpot idea that is half-baked even by crackpot standard. Thus, per the new PF Guildeline regarding this type of discussion, this thread is closed and you are welcome to submit your "classical" theory of metals to the IR section for review.

    Zz.
     
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