Quantum numbers of 25th electron of Fe, M=2, l=2, n=3 s=1/2 Is it correct or incorrect???

1 Answer
Truong-Son N.
Apr 25, 2018

Well... not quite.

Iron has a valence configuration of #3d^6 4s^2#. Four electrons among the last six are all degenerate, i.e. the #3d# looks like:

#underbrace(ul(color(red)(uarr) darr)" "ul(color(red)(uarr) color(white)(darr))" "ul(color(red)(uarr) color(white)(darr))" "ul(color(red)(uarr) color(white)(darr))" "ul(color(red)(uarr) color(white)(darr)))_(3d)#

So the NOT last electron is spin-up, and therefore could be in ANY of the five #3d# orbitals. Thus, the quantum numbers should be:

#n = 3, l = 2, m_l = {-2,-1,0,+1,+2}, m_s = +1/2#

So there are five sets of quantum numbers for this electron, not just one.

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