Determined the order of the reaction with respect to IO3- to be 1 and 1 respectively. The actual order of the reaction with respect to IO3- is 1. This along with your value for the order of the reaction with respect to S2O52- gives a rate law for the reaction of rate=k[IO3-]1[S2O52-]1.3

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.