You are given the melting points of three unknown substances and are asked to predict which one is an ionic compound. you would select the compound with the blank melting point

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.