What are the steps to dispose of contaminated material?

Engineers have contribute to society in many ways like making the technology we use today or any type of power energy material

Noble gases is far right

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.