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Atomic radius

  1. Nov 20, 2009 #1
    for the calculations in one of my homework questions, i need to use the atomic radii of Fe and Ni, the problem is that every site i come accross gives me different values

    Fe
    wikipedia 126pm
    physlink 1.72A
    chemicool 140pm


    how do i know which one to "trust" ?
     
  2. jcsd
  3. Nov 20, 2009 #2

    chemisttree

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    Is that zero valent iron and nickel or one of their ions?

    The ionic radii for ions are a function of their coordination number and oxidation #.
     
  4. Nov 21, 2009 #3

    Borek

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    I think I have seen such data on IUPAC site, even if it is not correct, source sounds as reliably as possible.

    No idea what is the definition of atomic radius, could be differences can be attributed to different understanding of what the atomic radius is.

    --
     
  5. Nov 21, 2009 #4

    chemisttree

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    It is likely the atomic radius in gas phase. Putting a metal atom in a metal lattice can change the radius as well.
     
  6. Nov 21, 2009 #5

    Borek

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    That's more or less what I am aiming at - depending on the way you want it, you will get different numbers. Even in the gas phase it is not obvious to me what 'size' means, as atoms don't end abruptly :wink:

    --
     
  7. Nov 22, 2009 #6
    im really confused,, the question goes like this

    find the plane density for the plane [1 1 1] of the following:

    iron (BCC)
    nickel (FCC)

    for [111] i know that
    BCC- R=sqrt(3)/4*a
    FCC- R=sqrt(2)/4*a

    PD=n/A

    BCC[111]- PD=sqrt(3)/(16*R^2)
    FCC[111]- PD=sqrt(3)/(6*R^2)


    now all i need to do is find the CORRECT radius to use, i used
    FE 126pm
    Ni 124 pm

    and got

    PD(Fe)= 6.818*10^-6 [atoms/pm^2]
    PD(Ni)= 1.877*10^-5 [atoms/pm^2]

    but i dont know if thats right
     
  8. Nov 23, 2009 #7

    chemisttree

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    Last edited by a moderator: Apr 24, 2017
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