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Ionic number for transition.

  1. Apr 11, 2004 #1
    oxidation number of transition elements.

    I know the oxidation number of non-metallic elements.
    But :confused:
    How do I know the oxidation number of transition elements.
    Such as Fe and Cr
    Cr = 4s1 3d5 when Cr change to Cr2+ Cr3+ Is it stable?
     
    Last edited: Apr 11, 2004
  2. jcsd
  3. Apr 12, 2004 #2
    The 2+ ions across the period start as strong reducing agents, and become more stable. The 3+ ions start stable and become more oxidising across the period.
     
  4. Apr 12, 2004 #3
    You can usually figure it out when given a compound. ie. FeCl3, Fe in this form has a +3 oxidation number, whereas in FeCl2 it would have a +2. However, many elements have a common oxidation state and this is often represented as bold type when looking at a periodic table that lists oxidation numbers.
     
  5. Apr 12, 2004 #4
    Thank you for your help. :smile:
     
  6. Apr 13, 2004 #5
    but how would you determine oxidation states in complex ions, or even organic compounds?
     
  7. Apr 21, 2004 #6
    Let me explain
    In complex ions you need to know EN in periodic table.
    high EN ion will absorb negative charge from lower EN ion.
    ie.

    SO4(2-) O have higher EN than S. O will be negative.
    SO4 have (2-) charge.
    O4=(:cool: charge

    (-8)-(-2)=-6
    now S will have +6
     
    Last edited: Apr 21, 2004
  8. Apr 21, 2004 #7
    what what about in organic molecules?
     
  9. Apr 21, 2004 #8
    transition metals have variable oxidation states, ie Cu +2 and 3+ etc, that whole point of transion metals is that they can have variable oxiadation states (because of the d orbital) any way, other wise most elements have fixed oxidation numbers, Oxygen is -2 becuase it is in group 6.
    as a general rule -
    Group : 1 2 3 4 5 6 7 8
    Oxidation No: 1 2 3 +-4 -3 -2 -1 0
    but yea it mostly depends what it is bonded to.
    so in CO2:
    O is -2 and there are two of them.. :. the -ve charge is -4.
    but its a molecule with no charge :. the oxidation No of Carbon must be +4
    ^which happens to fit in with what i had said b4 .
    -Deimos
     
  10. Apr 22, 2004 #9
    by organic molecules, did you meen hydrocarbons (alkenes/alkanes...), or things like CO2 , because thats an organic molecule
     
  11. Apr 23, 2004 #10
    CO2, I believe, is inorganic.

    Finding the oxidation states of organic compounds is easy. Just "explode" the structure, and by that I mean draw the compound with each element having is valence electrons around it. Then you have to decide who gets which electrons, the most electronegative element will get the electrons. In acetic acid, for example...The O has 6 valence, but it gets two from the carbon it is double bonded to (if it was a single bond, it would only get one), so now O has 8, giving it a oxidation state of -2. The O in OH also takes one electron from carbon, it has 7 valence now, giving it a oxidation state of -1. Carbon originally has four, but lost two to O, and another one to OH, so now it has 1, giving it a +3 oxidation state. The carbon adjacent to this one shares an electron with the other carbon, so that one doesn't lose any, and the carbon with a +3 state doesn't lose another one.

    I hope that made sense. That's how I was taught it. Look up exploding shell method (ESM).
     
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