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Why isn't the ion NH4+ capable of hydrogen bonding?

  1. Nov 17, 2014 #1
    If you draw lewis structure, central atom (N) will have 1 lone pair and 4 single bonds with Hydrogen.
    Why can't hydrogen in this ion molecule be able to form hydrogen bonding with other molecules alike?
    Is it because there's only 1 electron on the central atom?


    See for yourself: 5N + 4H -1 = 9 electrons to go around.
    4 bonds = 8 electrons
    9 - 8 electrons = 1 electron left.
    So this 1 electron is placed on the central atom.
     
    Last edited: Nov 17, 2014
  2. jcsd
  3. Nov 17, 2014 #2

    Borek

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    Staff: Mentor

    That's definitely wrong. No lone pair in NH4+.
     
  4. Nov 17, 2014 #3
    I've just updated my post. How can't there be?
    Nitrogen has 5 valence e + 4 Hydrogen valence e -1 from the charge sign = 9 electrons to go around.
    So... there's only 1 electron on the central atom?
     
  5. Nov 17, 2014 #4

    Borek

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    Staff: Mentor

    5+4-1 is 9?
     
  6. Nov 18, 2014 #5
    Yeah I dun goofed, sorry.
    Anyway, if this molecule was just NH4, and it had 9 molecules, would it be capable of hydrogen bonding? Since it would have a electron on its central atom...
     
  7. Nov 19, 2014 #6
    There is no atom orbital left to form a hydrogen bond. In NH4+ there are four binding sp³ hybride orbitals populated with each 2 electrons. An additional electron would be located in an anti-binding sp³ orbital resulting in a half bond for one of the four hydrogen atoms. I do not know if such a molecule exists, but it would be less stable than NH4+.
     
  8. Nov 20, 2014 #7
    Just imagine that the lone pair that is necesary to form hydrogen bonding which is present on NH3, it is not present on NH4+, becasue "it's forming the bond with the fourth hydrogen".
     
  9. Nov 20, 2014 #8
    However, that only means that NH4+ cannot form a hydrogen bond with another NH4+. But it can form a hydrogen bond with the electron pair of NH3 resulting in [H3N-H...NH3]+.
     
  10. Nov 23, 2014 #9
    Uhm... I said NH4 not NH4+
    What will the lewis structure be? Will it have 1 electron on the central atom?
     
  11. Nov 23, 2014 #10
    NH4 will not exist.
    If an NH3 molecule binds to another atom/molecule, a positive charge will be held by the nitrogen.
     
  12. Dec 2, 2014 #11
    But what would happen to a single left out electron in any atom where it's possible? Would it be placed on the central atom... or? Where would it go?
     
  13. Dec 13, 2014 #12
    It is more complicated than that, electrons are not placed in "concrete spots" of the molecules, you can say that they are in a given molecular orbital.
    But for sake of simplification, you can say that in that hypothetical situation, the electron could be on the central atom and you would have an ammonia/ammonium radical. A radical is a species that happens to have 1 single electron in one atom.
    This is not a common thing in a molecule like ammonia, but there are many radical forms of organic molecules, for example: http://www.masterorganicchemistry.com/2013/07/30/free-radical-reactions/
     
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