rubidium
Rubidium
Rubidium is much more reactive. It's a member of group 1 like sodium.
rubidium
Rubidium is highly reactive and if it is added to cold water there will be a large, exothermic reation; rubidium hydroxide and hydrogen are formed.
because rubidium has one valence electron while strontium has two.
Very soft and highly reactive.
Francium, caesium, rubidium
Magnesium
because it only has one electron on its outer shell
Francium, Cesium, Rubidium
Because they are extremely reactive to any moisture in the air.See the Related Questions about the reactivity of the alkali metals (rubidium and cesium are the most reactive of the alkali metals).