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Polyatomic ions

  1. Jul 15, 2004 #1
    Is there any theory as to why you have ClO-, ClO2-, ClO3-, and ClO4-, but only IO3- and BrO3- ? And why is there no FO3- ? I suspect this has something to do with electronegativety but I'm uncertain. And how come you have NO3-, but PO4 3-?
  2. jcsd
  3. Jul 15, 2004 #2
    Periodate and perbromate exist (IO4- and BrO4-). There is also H5IO6, HBrO, and IO-.

    You are correct. Fluorine is too small and too electronegative to be oxidized by oxygen. Fluorine is the only element more electronegative than oxygen.

    All the pnictides (nitrogen group) have different behaviors when it comes to oxidation states. But basically, the reason you have H3PO4 for P in the +5 O.S. and not HPO3 is because phosphorous has more electrons to take away than nitrogen. Nitrogen only has 7 electrons total, and only 5 valence electrons. Once there are three oxygens taking electrons away from nitrogen it's over, no more oxygens can fit. Phosphorous has 15 electrons total and there are more than the 5 considered to be valence electrons that are available to be taken by oxygen. Another thing that contributes to this electron grabbing is the greater difference in electronegativity between phosphorous and oxygen.
  4. Jul 16, 2004 #3


    Bill and Ted
  5. Aug 5, 2004 #4
    Well, it's not completely determined by number of electrons in the outer shell, because you can relatively easily make noble gas compounds like XeF6, but for all practicle purposes its just looking at what can make a full shell, or half full shell.
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