What was important about the copernican revolution? A. It was the first time a new theory was published in a book.

B. The scientific community never accepted it.

C. It demonstrated that scientific understanding was always changing.

D. It caused an immediate shift in accepted ideas.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

Bis the answerhope it !