Can someone show their work on how to do this: Calculate the number of moles of Al2O3 present in 23.87g. (Molar mass of Al2O3= 102.0g/mol)

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.