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Q & A: spin quantum number m

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Most recent answer: 03/17/2016
Q:
What is the spin quantum number for the last electron in Potassium (The 4S^1). How can we know whether it is +1/2 or -1/2.
- Parth Patel (age 18)
Etobicoke, Ontario, Canada
A:

The simple answer is that the ground state is degenerate, so there is no definite m value.  Measurement will be equally likely to find +1/2 or -1/2.

If you put the atom in a magnetic field, thereby breaking the degeneracy, the ground state's spin will tend to align with the magnetic field.

If we consider the spin of the nucleus there could be a preference for the 4S electron to align with it.  But that is a very weak effect, part of the "hyperfine structure."

Richard

 

 


(published on 03/17/2016)

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