# Help please, reallyy simple MCQ on Quantum numbers

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#1
Here it is :

I don’t know which fills first, the 4s or the 3d ? I thought it was 4s but a friend of mine says the answer is B not A so I’m not sure
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1 year ago
#2
(Original post by Leah.J)
Here it is :

I don’t know which fills first, the 4s or the 3d ? I thought it was 4s but a friend of mine says the answer is B not A so I’m not sure
The last electron theoretically added is the 3d10 electron... unless you are coming from copper [Ar]4s1 3d10, in which case it would be the 4s2 electron.

The question is actually nonsense, as electrons are not "built up", but rather exist in the arrangement found empirically in each species. It like saying that protons are "added" when moving up the periodic table.

It's a poor question, open to different interpretations.

In terms of logic,
Choice A is energy level 3, d sub-shell, fourth orbital, up-spin (not possible, as 3d orbital chosen for final entry should be -2 and spin -1/2)
Choice B is energy level 4, s sub-shell, s orbital, up-spin (not possible, as wrong electron added, should be -1/2)
Choice C is energy level 3, s sub-shell, s orbital, down-spin (not possible, as 3s!)
Choice D is energy level 4, p sub-shell, pz orbital, up-spin (not possible, as no 4p in zinc)
Choice E is energy level 4, d sub-shell, dz2 orbital, down-spin (not possible, as 3d not 4d)

hence, rubbish question

The answer should be: n=3, l=2, m=-2, s=-1/2
Last edited by charco; 1 year ago
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