Net ionic equations supply chemists with information about which forms of the reactants actually undergo a chemical change. For a chemical change to happen, there must be a driving force, and frequently that driving force is when substances form chemical precipitates. Having the ability to write out net ionic equations is an important way to be able to recognize which substance is a solid and which may be a strong electrolyte. The strong electrolytes are the spectator ions in a solution, and serve important functions in the human body. That is why it is important to replenish these electrolytes after exercise. There are a few ions on which you can always count to be soluble in water; therefore, they are the spectator ions. These are sodium ions, nitrate ions, and potassium ions.