Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Lewis and polyatomic ions

  1. Nov 11, 2003 #1
    Hi everybody, im new to PF and thus far have found it very intresting and helpfull.

    I have a chemistry question, my test is tomorrow.

    I know how to draw lewis strutures in general. But i have a question concering polyatomic ions,

    from what i have learned you should treat each ion seperatly.

    but on the compound KH2PO4 the struture looks like thus
    H--O O
    \ / (the lines should contect the p to the o's
    P but for some resonce i cant make it work)
    / \
    H--O O
    sense PO4 is an polyatomic ion why isnt is seperate

    my other question (which more critically of the two) is the structure of HCN and HN03

    in both of the stutures the h is attaced to the struture. But both contain polyatmoic ions, cyanide and nitrate.

    why are they seperate?

    Does have something to do with them being acids( my not sure if they are acids, we have not covered acid in my chem text yet).

    thank you for your help

    Last edited: Nov 11, 2003
  2. jcsd
  3. Nov 12, 2003 #2


    User Avatar
    Science Advisor

    The PO4 is not separated from the H2 because H2PO4 is itself a polyatomic ion.

    HCN and HNO3 separate because they are not polyatomic ions; they are simply acids just as you said :).

    Here is a list of polyatomic ions for future referance
    http://www.woodrow.org/teachers/chemistry/links/chem1/PolyatomicIonsChart.html [Broken]
    Last edited by a moderator: May 1, 2017
  4. Nov 12, 2003 #3
    thank you for your help. The list of polyatomic ions i was using is small and only contains a few of the hundrens of them out their. Thank your replie and the list.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook