3d fills before 4s???

[junkct]

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Doesn't this violate the n+l rule? Does this happen with any other sets of subshells?

 

[BerkReviewTeach]

Doesn't this violate the n+l rule? Does this happen with any other sets of subshells?

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.

 

[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...

 

[Phlame217]

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.