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GC question topscore

Discussion in 'DAT Discussions' started by rocky90, Aug 1, 2011.

  1. rocky90

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    Can anyone please tell me the quantum numbers for the highest energy electron in fluorine.
    Isnt it supposed to be n=2, l=1, ml=0 ms=-1/2 ?
    Thanks
     
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  3. toothhornet88

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    yes thats correct

    also found this site...dont know if it will be any useful

    http://oi56.tinypic.com/zno2s7.jpg
     
    #2 toothhornet88, Aug 1, 2011
    Last edited: Aug 1, 2011
  4. PooyaH

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    That's correct, but it also could be:

    n=2, l=1, ml=1/-1, ms=1/2 or -1/2
     
  5. rocky90

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    According to topscore the answer is n=2, l=1, ml=+1, ms=-1/2 which I dont get how. The last electron in fluorine is the highest energy electron (please correct me if I am wrong here) and thus should be n=2, l=1, ml=0, ms=-1/2.
    I would think that saying n=2, l=1, ml=+1, ms=+1/2 would be wrong too, since it is not the highest energy electron. Any help would be appreciated.
    Thanks
     
  6. rmm30

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    I'm not sure i agree with either topscore or you on this one. I think both answers are correct and the question is worded poorly. First of all, lets ignore Ms for now, seeing as how its arbitrary. What you have next is the quantum numbers for Shell :thumbdown: Subshell (l) Orbital. n=2 and l =1 are obviously correct. But the magnetic number Ml is where I have a problem. This number defines the orbital which you are in. Orbitals of the same Shell and Subshell are degenerate i.e. they have the same energy. That's why "the highest energy electron" sounds inaccurate. Both of those answers should be correct. And as Pooyah said,Ml could even be -1. It would still be correct
     
  7. LetsGo2DSchool

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    The l number pertains to the p-orbital. There are three of these px, py, pz. They are all degenerate orbitals meaning they are equal in energy level. Thus, an ml number of -1, 0 ,+1 are all the same. The numbers are only a designation, just like there is no difference between an electron that is +1/2 or -1/2.

    Thus, there is no difference in energy level among the three scenarios you listed above.

    I think you should read the chapter in a gen. chem textbook regarding this topic. It seems like your understanding is a bit fuzzy and thus, you're getting more confused by reading the solutions.
     
  8. rmm30

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    i think you mean that l number designates the p subshell ( not orbital ). ml represents the orbitals in the subshell. remember when dealing w quantum #s Shell, Subshell, Orbital, electron; But yeah that other stuff seems correct to me
     
  9. LetsGo2DSchool

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    Of course, the p subshell are the p orbitals. For example:

    n = 2 (second shell)

    l = 1 (subshell -- p orbitals)

    ml = -1, 0, +1 (px, py, pz -- all degenerate orbitals -- no difference)

    ms = -1/2, +1/2 (no difference -- just means that one electron is spinning in one direction and the other electron is spinning in the opposite direction -- it's the only way two negatively charged electrons can reside in the same orbital without repelling each other)
     
  10. rocky90

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    Actually I am pretty sure about this and I remember asking about this while taking gen chem back in those days. To get the ml number if we draw the box for say p orbital the left side is -1 the middle is 0 and the right is +1. As per Hunds rule all electrons go +1/2 first followed by antiparallel (ms=-1/2) pairing. So if asked for a particular electron it has to be a specific quantum number since according to Paulis exclusion principle no 2 electrons can have the same set of quantum numbers. The degenerate orbitals deal with stable configuration (not highest energy electron) when their are maximum number of electron with parallel spin. But regardless every electron will have a set of quantum number. Maybe it might be different if topscore is saying that the last electron is not the highest energy electron but it still doesnt make sense as for fluorine their are no electrons in the ml=+1 and ms=-1/2. I hope you can see why this is confusing me and is not making sense.
    Thanks.
     
  11. needzmoar

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    The problem with this reasoning is that the axes are arbitrarily defined, that is, you can't say the electrons go in ml=-1 first or ml=1. I do, however, agree that this top score question lacks clarity.
     
  12. rocky90

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    If this is really true then my gen chem prof was totally wrong as this is what he told us in class. I still have a question like this (not same though) in my gen chem notes asking for the exact quantum number for an electron and exactly fits this model and answer choice...:idea:
     
  13. LetsGo2DSchool

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    I am absolutely 100% sure of this as I specifically confirmed this with my GChem professor on this topic last year. GChem is also my strongest subject btw. In accordance with the Hunds Rule, it doesn't matter whether you start with ms= +1/2 or -1/2 as long as they are consistent as you fill up the orbitals. So for example, say we had 4 electrons to fill the p orbitals, they could be filled in either order:

    +1/2, +1/2, +1/2, -1/2

    or

    -1/2, -1/2, -1/2, +1/2

    You're getting caught up in the +/- sign which are just arbitrary designations for ml and ms and have nothing to do with a higher/lower energy.
     
  14. needzmoar

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    Well, I'm not saying he's wrong. I'm sure he there was a reason why he labeled it that way. Perhaps for consistency with the rest of his lecture notes? Maybe he was just trying to reinforce that ml = -l....0....l so he labeled the orbitals accordingly. Maybe the 'trick' to this problem is to eliminate all of the wrong answer choices.
     
  15. rocky90

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    Is that also true for ml? Means it can go into either +1 or 0 or -1 in any order. In that case if I am understanding it right either one could have been the correct answer and there are two right answers in the questions then. Is that correct?
    Thanks
     
  16. rocky90

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    Well he caught me then :smuggrin:. I think I had asked him about this too and he had agreed to it back then. What a stupid rule to follow though, my notes are full of this crap. :smuggrin:
     
  17. rmm30

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    Yeah. Except there are 6 right answers ml = -1 or 0 or 1 and ms = + or - 1/2
     

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