3d fills before 4s???
Started by junkct
4s fills before 3d. Just look at the periodic table to confirm this. As for the n + l rule, you are probably better off following the filling order using the periodic table, because you know you'll get one on the MCAT and it shows the exceptions that such a rule might miss.
However, where it gets a bit tricky is that when a transition metal becomes a cation, it loses s-electrons before losing d-electrons.
hm, wouldn't this imply that 4s is higher in energy then? in which case, wouldn't it fill AFTER 3d?
I was doing a kaplan topical test about exceptions to the aufbau principle and this came up multiple times...
Remember this pattern: http://www.steve.gb.com/images/science/orbital_filling.png
Also!!! For transistion metals, remember that 3d and 4s are so close in energy, that the electrons that initially double up in the s orbital can bounce between the d and s orbitals especially in elements like Cr. This is due to the principle that electrons will first fill all orbitals in the same spin before they double up.
Also!!! For transistion metals, remember that 3d and 4s are so close in energy, that the electrons that initially double up in the s orbital can bounce between the d and s orbitals especially in elements like Cr. This is due to the principle that electrons will first fill all orbitals in the same spin before they double up.
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