What is the number of nitrogen molecules that reacted with excess hydrogen to make 2x10^10 molecules of ammonia

Um try B? i think that would be correct. either B or C

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.

The answer for this is a