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Homework Help: Which elements travel in pairs ?

  1. Aug 30, 2006 #1
    Which elements "travel in pairs"?

    This isn't exactly "homework help", just something that's been on my mind for a while. I know that when writing chlorine, oxygen and hydrogen by itself, you need to add a two. Why is this so? And also, what other elements "travel in pairs"?
  2. jcsd
  3. Aug 30, 2006 #2
    the halogen and the inert gases "travel in pairs." bromine, iodine...Xe...
  4. Aug 30, 2006 #3
    Aha...answer found here. This thread can be closed :)
  5. Aug 30, 2006 #4
    Consider also:

    phosphorous- P4
    arsenic- As4
    sulfur- S8 and others
  6. Aug 30, 2006 #5


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    Staff Emeritus
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    Inert (noble) gases are monatomic.

    H, N, O, and halogens F, Cl, Br, I, At form pairs, or diatomic molecules.

    Cesium gave forms in which molecules have quadruples or octuples.
  7. Sep 9, 2006 #6
    Question related to this.....

    Halogen and such gases exists in diatomic - we write Cl2, I2 etc.
    But sulphur exist in S8, why we write S in our equations?
    then when do we write as element (in S) and when we write in molecule as in Cl2?

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