# Which electron configuration is not possible for As? Don't know much about spdf orbit

1. Oct 8, 2008

### lost_in_phys

11. Which one of the following sets of quantum numbers (n, l, ml, ms) could not possibly describe one electron of an arsenic atom (Z = 33) in its ground state?

(A) 2, 1, -1, 1/2
(B) 4, 2, 2, -1/2
(C) 3, 0, 0, -1/2
(D) 3, 2, -2, 1/2
(E) 4, 1, 0, 1/2

Solution:

Electron configuration for arsenic:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p3

2, 1, -1, 1/2 represents a 2 p electron, possible.
4, 2, 2, -1/2 represents a 4 d electron, NOT possible for As.
3, 0, 0, -1/2 represents a 3 s electron, possible.
3, 2, -2, 1/2 represents a 3 d electron, possible.
4, 1, 0, 1/2 represents a 4 p electron, possible.

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I don't understand why its the second one, I do know that all of the numbers are allowed for n, l, ml, ms, but i dont understand how it changes when the element As comes into play.

Thanks for any help

2. Oct 9, 2008

### Staff: Mentor

Re: Which electron configuration is not possible for As? Don't know much about spdf o

Does As have electrons on 4d when in ground state?

3. Oct 9, 2008

### lost_in_phys

Re: Which electron configuration is not possible for As? Don't know much about spdf o

Oh ok, that's what i didn't understand in quantum numbers, l of 2 indicates a d orbital, but as has no electrons in a d orbital in ground state. thx

4. Oct 9, 2008

### Staff: Mentor

Re: Which electron configuration is not possible for As? Don't know much about spdf o

Yes it has - but on 3d, not 4d.

5. Oct 9, 2008

### lost_in_phys

Re: Which electron configuration is not possible for As? Don't know much about spdf o

Sorry, yea, thats what i meant, thx