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Topic: Term Symbols  (Read 6975 times)

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Offline ahhppull

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Term Symbols
« on: March 25, 2013, 07:29:31 PM »
I need some help with term symbols. I'm not entirely sure on how to do these.

What are the possible term symbols for the following electron configurations?
1) 1s2 2s2
2) 1s2 2s1 3s1
3) 1s2 2s2 2p2

For #1, I got 2P1/2
For #2, I'm not sure how to do this.  It is in an excited state?
For #3, I got 2P1/2 and 2P3/2

Offline Corribus

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Re: Term Symbols
« Reply #1 on: March 25, 2013, 07:37:11 PM »
Term symbols: the bane of every p-chem student's existence.  I remember leading TA sessions on the topic and by the time we were done - hours later - both the students and myself needed some serious quantities of beer. 

I'd say the first thing to do is realize that a given electron configuration typically has more than one term symbol associated with it, because there are multiple electronic states that can have the same general electron configuration.

That realized, you need to write out every possible microstate for that electron configuration, THEN figure out the term symbol associated with that group of (identical) microstates.  There is actually a pretty nice step-by-step guide available at wikipedia.

http://en.wikipedia.org/wiki/Term_symbol

Check it out, see if you can't figure your problems out, then come back with additional questions. 
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline ahhppull

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Re: Term Symbols
« Reply #2 on: March 25, 2013, 08:10:40 PM »
Thanks for the link!

So after reading the wiki, I found out that #1 should be 1S0.  For #3, it was the same example used, and I almost fully understand it.

What about #2?  Is it the same procedure as #3?


Offline ahhppull

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Re: Term Symbols
« Reply #3 on: March 25, 2013, 08:21:50 PM »
I also have another homework problem.  It asks for the possible term symbols for ground state of chlorine.

So by following the procedure in wiki, there should be 6 microstates.

 :spinpaired: :spinpaired:  :spinup:      ML = 1 MS =1/2
 :spinpaired: :spinpaired: :spindown:   ML = 1 MS =-1/2
 :spinpaired:  :spinup: :spinpaired:      ML = -1 MS =1/2
  :spinpaired: :spindown: :spinpaired:  ML = -1 MS =-1/2
 :spinup: :spinpaired: :spinpaired:       ML = 0 MS =1/2
 :spindown: :spinpaired: :spinpaired:   ML = 0 MS =-1/2

I haven't finished the problem, but am I on the right track?

Offline Corribus

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Re: Term Symbols
« Reply #4 on: March 25, 2013, 08:41:37 PM »
Looks like you're on the right track.
Also, for closed shell atoms in their ground state, the term symbol is always 1S0.  Easy shortcut to remember. :)
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

Offline ahhppull

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Re: Term Symbols
« Reply #5 on: March 25, 2013, 08:42:48 PM »
Looks like you're on the right track.
Also, for closed shell atoms in their ground state, the term symbol is always 1S0.  Easy shortcut to remember. :)

Thanks, I figured it out, but I still am unsure of what to do for #2 where the electrons are in an excited state.  Since its not in the ground state, its not 1S0Do I follow the same procedure as the previous problems?

Offline Corribus

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Re: Term Symbols
« Reply #6 on: March 25, 2013, 09:27:37 PM »
Yes, you follow the same procedures.  Just write out what all of the possible microstates are (all the orbital combinations) and you can't really get into trouble.  I always found it help to tabulate it all in the manner shown in the wikipedia article.  It was pretty hard to screw it up when you do it that way.
What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?  - Richard P. Feynman

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