Chemical Forums
Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: hiddentempo on March 20, 2012, 12:23:36 AM
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Could someone please explain to me how to build a microstate table? I know it is probably pretty simple but I'm just not getting it. I'm a little rusty with the Aufbau and Pauli exclusion principles so no worries in being too basic. Also, determining the atomic states from the table is a little rough for me too. Final on wednesday.... :-\
I know this seems broad but I can't even get started. I'm not sure where to even get L, really.
Also, something that has always confused me about M.O. diagrams: when building the diagram "according to symmetry matches," which orbitals exactly are we matching up? So in a diagram of CO2, do I take all the orbitals from Carbon and see which one "match" O? And by symmetry matching does that mean that they're in phase?
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Are you Irish? Anyhow, I've been learning this myself lately. So to make a microstate table of a particular configuration, first look at how many electrons you're dealing with (it'll probably be 2 cuz any more than that and the microstate table would be massive) and what orbital it is. Lets say the configuration is p2. This means you have 2 electrons in each of the 3 p orbitals. A microstate is just the word for a particular configuration of each of the 4 quantum numbers. You don't care about the first 2 quantum numbers since they're fixed, only ones you care about are ml, the magnetic quantum number and ms, the spin quantum number. ml tells you which of the 3 p orbitals the electron is in and it can be +1, 0 or -1. ms is the spin of the electron which can be either +1/2 or -1/2. Lets say for some reason both electrons are paired (which wouldn't happen cuz according to Hunds rule, unpaired electrons are more stable), then we can represent this microstate like this: (1+,1-). 1+ represents one of the electrons and it means that the electron is in orbital 1 and has a + spin.
ML is the sum of the ml values for this microstate and MS is the sum of the ms values for the microstate. So for this particular microstate, ML = 2 and MS = 0. So a microstate table is just a table of all the possible microstates of a particular configuration. For 2 electron configs, there will always be 3 columns because by adding the spin values which can be either +1/2 or -1/2, there is only 3 values you can get, 1, 0 or -1 so thats what label your columns with (i.e. the columns are for MS values). The rows are for ML values and since there are 3 different ml values to add together, you can end up with either 2, 1, 0, -1 or -2. So thats what you label the rows with. Thats pretty much it. Thats all there is to microstate tables. If you wanna know how to derive the terms from a microstate table, tell me and I'll explain it cuz this is good revision for me.