Plss
what is the difference between the rate of dissolving and solubility? ?

Solubility

It is a Quantitative term that defines the maximum amount given substance that could be  Dissolved in the solute given It is thermodynamic entity .Solubility measured in mol/kg The concentration of the solute, System's temperature, pressure and the polarity of the solvent and the solute are the factors affecting the solubility  

Dissolution:

The process by which a solute(substance) undergoes interaction with each other and gets dissolved in a given solvent due to an increase in the  stability. It is kinetic entity .Dissolution is measured terms of mol/s Processing factor, factors related to dissolution apparatus, drug product formulation, physiochemical property affects the dissolution

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.