What is the mass, in grams, of 2.11 mol of sulfur trioxide?

Ithink it’s 3 as the answer.

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.

Anions are negative charged ions

Just took the quiz on edgenuity and the correct answer is "c.  4.54 x  10–12  j"