Is the Aufbau principle violated in the diagram (b)?


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> In which of the following diagrams is the Aufbau principle violated?
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> ![enter image description here](https://i.stack.imgur.com/qUohQ.jpg)
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Ignoring the Hund principle, the Aufbau principle states that electrons have to first fill the lowest energy levels. Now the energy level of the s-orbital has to be the lowest, and only in the option (b) the s-orbital is not filled fully. So the answer is (b).


Is my reasoning correct?




Since the question specifically asks about the violation of [Aufbau principle](https://en.wikipedia.org/wiki/Aufbau_principle), your reasoning is correct. 


Had it been based on the violation of [Hund's rule](https://www.chem.purdue.edu/gchelp/gloss/hundsrule.html) then option (a) would be the answer.


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