Calculate the millimoles of barium chlorate the chemist has added to the flask.

If you are given the concentration of the solution in the flask in terms of molarity, then you can easily determine the moles of barium chlorate in the flask by multiplying the volume of the solution to the molarity. Then, multiply the resulting value to 1000 to obtain millimoles of barium chlorate. However, if you are given the mass of the barium chlorate added. You use the molar mass of the compound which is 304.23 g/mol to determine the number of moles. You divide the mass with the molar mass of the compound. Then, you multiply it to 1000 to obtain millimoles.

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.