Laura has three beakers. Each contains 200 cm3 of a colourless liquid. Suggest how Laura could nd out which beakers contain pure water, and which contain solutions.

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.

Maybe you should get some from your teacher and learn more so you can get your grades up and maybe study a bit more