Ever heard of this thing called... RESEARCH!? You might want to try it buddy. Sayounara.
Once the substance stops dissolving, the system is at equlibrium with the water and the undissolved salt now, if it is in the process of dissolving because it is completely soluble but has not been able to completely dissolve, it is not at equilibrium
First off chlorine is not a metal so you can ignore that one.
Sodium and Rubidium are in group 1 of the periodic table and Magnesium is in group 2.
Group one metals are more reactive than group two because it is harder for the group two metals to lose their 2 valence (outer most) electrons.
As you go down group 1 there is an increase in the reactivity this is because as you go down there is an increase in the atomic radius which leads to more shielding. This weakens the electrostatic forces of attraction making it easier to lose the outermost electrons, therefore they are more reactive.
DSVR because it only makes sense. Try it out and if it works give me a Brainly