Mayonnaise is made of egg vinegar and oil under which category could it ne classified in a. elements b. compounds c. solutions d. colliods

I believe that the answer you have that best answers the question would be a compound. Because mayonnaise are not an element on the periodic table, and not a colloids. That leaves a solution or a compound, a solution is the distribution of particles evenly while a compound is simply combining things.

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.