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Atom space

  1. Jul 5, 2011 #1
    how close are the atoms in any solid, is all the space possible in a solid is filled up by its atom finally can we consider an atom an isolated body ,or can size of strings pass between inter atomic spaces.i believe atoms in the solid is not actually in contact but there exists infinitsimally small distance in them.
     
  2. jcsd
  3. Jul 5, 2011 #2
    There you carry with you a lot of clandestine postulates.
    Let's try to disclose them.
    You postulate that atoms are kind of solid spheres, balls, maybe with strings between them.
    You think that between these solid balls, there is vacuum in-between.
    Nothing such exists.
    Each of the electronic cloud forming any isolated atom (in vapor) is fuzzy.
    In a molecule or a crystal, these fuzzy electronic clouds interact.
    In a covalent solid such as diamond carbon or boron, the bonds are sharing of pairs of electrons, with antiparallel spins, with strong spatial orientations. Diamond carbon and boron are stiff to shear stress.
    In the quartz, the bond between Oxygen and Silicon is partly covalent, partly ionic, so the bulk of the volume is Oxygen, with small cations.

    In metals, the bond is the metallic one, where the valence electrons form a pool, very mobile, where each one is several tens of interatomic distances long and wide, running at the Fermi speed, and bouncing from phonon to phonon, or other crystalline defects.

    At 0 K, in a perfect crystal, each conduction electron should be as wide as the crystal itself.

    In metals, the metallic bond is not spatially oriented, that makes dislocations so easy to produce and move, and makes the metals so plastic.
     
    Last edited: Jul 5, 2011
  4. Jul 10, 2011 #3

    edguy99

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    Gold Member

    One way to do this calculation is based on the density of the solid and the mass of each individual atom in the solid.

    Consider copper: Density=8.94 g/cm^3, AtomicWeight=63
    using a formula ((density/0.00166)^-1/3*1000)/atomicweight you get a spacing of 227 picometers between each atom. Certainly a "large" space considering what is thought to be a maximum "size" of an individual atom. This formula assumes the atoms are arranged in squares or a n-n-n shape. Most solids do not have an exact square shape (hexagonal or face centered cubic for example), but the "average spacing" will work out to be "about" the same.

    Consider a few other elements:
    Lithium, AW=7, density=0.534 =>> 279 picometer spacing
    Beryllium, AW=9, density=1.85 =>> 201 picometer spacing
    Carbon, AW=12, density=3.5 =>> 179 picometer spacing
    Silicon, AW=28, density=2.33 =>> 271 picometer spacing
    Gold, AW=197, density=19.3 =>> 257 picometer spacing
     
  5. Jul 10, 2011 #4
    It seems that the original question was not the interatomic distance, but what can be between atom-balls.
    For the copper (face-centered cubic), let's do the exact calculation :
    8940 kg/m^3 means 8940 x 6.022 E26 /63.55 atoms/m^3 =8,47 E28 atoms /m^3 = 2.12 E28 cell/m^3.
    Each cell volume is 47.2 E-30 m^3.
    So its edge : a = 0,361 nm,
    And the shortest interatomic distance, is the length of the [0, 1/2, 01/2] vector, that is a/[itex]\sqrt{2}[/itex] = 0,256 nm.
     
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