What is the volume in (in. Cm^3) of a 25.2g piece of metal with a density of 8.75g/cm^3

C) electrons encircling a nucleus with neutrons and protons

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.