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.
A) Double replacement
Because the reactants switch when they become products
The variable that stays the same in an experiment is called the controlled variable
Hope this helps
Newton's third law of motion states that for every action force, there is an equal and opposite reaction force so that means that the wall is pushing you with the same amount of force that you put on it.
