What is the basis for exceptions to the aufbau diagram?

Question

Also, If three electrons are available to fill three empty 2p atomic orbitals, how will the electrons be distributed in the three orbitals?

Answer 1

the simple answer to your question is just putting unidirectional electrons in the p-orbital. but a more complicated way of how the aufbau principle is disregarded is when there is hybridization of the orbitals together. you get s orbitals and p orbitals fuzing to create sp, sp2 and sp3 orbitals. but dealing with those are only needed when knowing the actual 3-D shape of the molecule.

Answer 2

If it violates the octet rule then exceptions must be made.

the 3 electrons would each go in a seperate 2p orbital with the same spin. (Hund rule)