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Classifying Ionic Compounds

  1. Nov 26, 2008 #1
    1. The problem statement, all variables and given/known data

    Which of the following compounds are properly classified as ionic? (select all that apply)
    HOCN
    SF4
    NH4NO3
    MgCl2
    K2O
    Li2
    NF3

    2. Relevant equations

    n/a

    3. The attempt at a solution

    My initial choices were MgCl2 & K2O ... however, since this was incorrect (it didn't tell me which were correct or incorrect - the entire problem was either correct or incorrect)... I'm guessing that HOCN and NH4NO3 might also classified as ionic.

    If this is true, what is the general criteria for recognizing ionic compounds (if the compound has more than 2 types of atoms)?

    Thanks!!!
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Nov 27, 2008 #2

    Borek

    User Avatar

    Staff: Mentor

    Second for sure, not so sure about the first one.

    In the case of binary compounds - large difference in electronegativity. In the case of more complex compounds - almost all salts are ionic.
     
  4. Nov 27, 2008 #3

    epenguin

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    Homework Helper
    Gold Member

    Li2?
    Am I the only one who has never heard of that?

    Is it something that can/does significantly exist in some laboratory in gas phase?
     
    Last edited: Nov 27, 2008
  5. Nov 27, 2008 #4

    Borek

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    Staff: Mentor

    I believe I have seen not only Li2, but also Na2 and K2 reported in gaseous phase. But don't quote me, I can be wrong.

    Edit:

    K2 at webelements:

    http://www.webelements.com/potassium/bond_enthalpies.html

    Not exactly what we are talking about, but an obvious sign that there are many exotic diatomic molecules.
     
    Last edited: Nov 27, 2008
  6. Nov 28, 2008 #5
    On the same note as NH4NO3, I found that HOCN can be expressed as two different ions as well: H+ and OCN-. Does that make it an ionic compound then?

    I'm confused because the individual atoms are covalently bonded...
     
  7. Nov 28, 2008 #6

    Borek

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    Staff: Mentor

    Not necesarilly. Gaseous HCl is covalent, but it easily dissociates into two ions.
     
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