Ligand Field Splitting

Discussion in 'Pre-Medical - MD' started by BlackSails, Apr 16, 2007.

  1. BlackSails

    2+ Year Member

    Joined:
    Apr 4, 2007
    Messages:
    865
    Likes Received:
    3
    Status:
    Pre-Medical
    Ok, so my teacher did not explain this so well.

    Basically, from what I see, is this:

    A ligand induces the outermost d orbital to split into the t2g and eg orbitals. The energy difference between them is noted as Delta0. Delta0 varies based on the ligand, and is not findable a priori, without computers. You look Delta0 up in the spectrochemical series. If Delta0 is greater than the energy difference between the singlet and triplet states, then the electrons pair up in the t2g level. If it is less, then the spins are aligned, and the electrons do not pair up until the eg level is also half full.

    Have I missed anything?

    Also, what is the difference between ligand field theory and crystal field theory in terms of ligand-transition metal interactions?

    Thanks!
     
  2. Note: SDN Members do not see this ad.

  3. Instatewaiter

    Instatewaiter But... there's a troponin
    10+ Year Member

    Joined:
    Apr 28, 2006
    Messages:
    5,899
    Likes Received:
    1,816
    Status:
    Attending Physician
    go to office hours
     
  4. Nevadanteater

    Nevadanteater biochemical engine
    7+ Year Member

    Joined:
    Jun 18, 2006
    Messages:
    306
    Likes Received:
    2
    MDApps:
    Status:
    Pre-Medical
    Physical Chemistry is a huge part of the reason i've left chemistry.

    eeeeew.

    I might (that's a big might) have been able to answer that about 4 years ago. Now PChem has been regulated to a part of my brain reserved for repressed memories and childhood embarassments.

    i agree - go to office hours. or use a chemistry board to get homework help - SDN doesn't have that many pchem heads...
     
  5. BlackSails

    2+ Year Member

    Joined:
    Apr 4, 2007
    Messages:
    865
    Likes Received:
    3
    Status:
    Pre-Medical
    This is for gen chem, not pchem :(

    Id go to office hours, but I think I would get the same vauge information that was in the powerpoint.

    I guess ill try wikipedia.

    Thanks though!
     
  6. DrMontana

    5+ Year Member

    Joined:
    Jan 25, 2007
    Messages:
    32
    Likes Received:
    0
    Status:
    Medical Student
    Try to find a pchem or inorganic chem book in the library. they'll go a little more in depth, but it might help.
     
  7. MeCord3

    2+ Year Member

    Joined:
    Nov 11, 2006
    Messages:
    69
    Likes Received:
    0
    Status:
    Pre-Medical
    You seem to have a grasp of it. I'm surprised you'd be covering this in gen chem. This seems much more suited to a Pchem or a quantum chem class. To answer your latter question, Ligand Field Theory evolved from Crystal Field Theory as it was combined with data arising from Molecular Orbital Theory.
     
  8. BlackSails

    2+ Year Member

    Joined:
    Apr 4, 2007
    Messages:
    865
    Likes Received:
    3
    Status:
    Pre-Medical
    Gen Chem honors at my school is.....thorough, in the same uncomfortable way that a strip seach might be.

    I do not exaggerate when I say that 1st semester drove students to the student health center for psychological help. The professor that semester was great, but he went a little quickly for the class' taste.
     
  9. chortlehortle

    chortlehortle Junior Member
    2+ Year Member

    Joined:
    Jul 5, 2006
    Messages:
    14
    Likes Received:
    0
    Status:
    Pre-Medical
    This seems mostly right...

    I just don't see how this is useful in the least bit for a Gchem class..

    I guess it gives you an idea of MO theory and how electron orbital/filling nature can be variable. But honestly, I could've just told you that without this erudite example of crystal field theory.

    Geez, what has become of GChem these days.

    But if you get it and all, then good for you. I tutored Gchem for 3 years and most of the students had a hard enough time understanding gram to mole conversions...:laugh:


    jk... (but not really for some people)
     
  10. Revilla

    Revilla New Member
    5+ Year Member

    Joined:
    Jul 22, 2006
    Messages:
    1,076
    Likes Received:
    3
    Status:
    Medical Student
    My Gen Chem II class is covering this very topic right now. It's part of the coordination chemistry concepts. We're only expected to know the basics about it though and our teacher gave us a totem pole of sorts for the most common ligands on the strong-weak fields.

    Sorry I can't be of more help, OP. We just started the unit, so I don't know much. It's just nice to know someone else is learning it too because none of the Gen Chem sections covered this last semester and very few are covering it this semester.
     
  11. crimsonkid85

    7+ Year Member

    Joined:
    Jul 3, 2006
    Messages:
    817
    Likes Received:
    235
    Status:
    MD/PhD Student
    at least from what i remember from inorganic chemistry, crystal field theory was developed to consider metal ions in crystals, and thus is called crystal field theory, but it is also useful for molecular coordination compounds of transition metals.

    ligand field theory uses molecular orbitals to consider a ligand environment of Lewis bases in an octahedron around a metal center.
     
  12. NoktorNoL

    NoktorNoL Member
    5+ Year Member

    Joined:
    Jul 17, 2006
    Messages:
    209
    Likes Received:
    0
    MDApps:
    Status:
    Resident [Any Field]
    You've got the gist of it..I assume since this is for Gen Chem that the simplified version you explained is adequate.

    Ligand field theory uses molecular orbital theory to explain the splitting...which means it assumes there are actually bonds between the ligand and the metal, and uses a lot of math to explain the nature of those bonds. Crystal field theory basically just "looks" at the splitting through magnetics and spectrophotometry and classifies the states as high-spin or low-spin based on its diamagnetic or paramagnetic properties.
     

Share This Page