filling up p orbitals

Question

a homework question was: when filling up the three p orbitals with electrons, Px has preference. I chose false which was correct, but I wanted clarification. there is no order of x, y, and z for filling them, correct?

Answer 1

The reason that there's no preference is because we, humans, have arbitrarily assigned the p_x,p_y, and p_z according to the Cartesian coordinates of x, y, and z. They are all equal in energy (if all empty, all 1/2 full, or all full). Hence, an electron added to empty p orbitals "goes" wherever it "wants". We tend to put it in the p_x first because of the alphabetical order of x, y, z.