What is the stationary phase in chromatography?

These are the two phases involved in chromatography. The mobile phase is usually liquid and is the solvent between the two. The solvent can attract some substances that has an affinity to it, thereby separating the polar from the non polar substances. On the other hand, the stationary phase is the media or medium which is a solid substance in which the unknown sample or the solution to be analysed is passed. As the term implies , it is stationary and substances in the unknown sample that has affinity to it or to the reagents in it will not travel along the column, but stay with the stationary medium, thereby allowing a separation of the substances present in the unknown sample/solution.

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.

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