A 1.044 g sample contains only vitamin C (C6H8O6) and sucralose (C12H19Cl3O8). When the sample is dissolved in water to a total volume of 33.0 mL, the osmotic pressure of the solution is 3.69 atm at 295 K. What is the mass percent of vitamin C and sucralose in the sample?

Abbreviated as mg-25.

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.