An aqueous solution has a mass of 490 grams containing 8.5×5103 gram of calcium ions. the concentration of calcium ions is in this solution is

There are several various of expressing concentration. For instance, mass percent, volume percent, Molarity, Normality, Molality, etc.

In present case, weight of solute and solvent are given, so it will be convenient to express concentration in terms of mass percent.

Given: weight of solute (Ca2+) = 8500 g
weight of solvent (water) = 490 g.
Therefore, mass of solution = 8500 + 490 = 8990 g

Now, mass percent = 
                               =
                               = 94.55 %

 Concentration of calcium ions is in this solution is 94.55 % (w/W)

Both models are effective because they show the valence electrons, and these valence electrons indicate the reactivity of an element.