What is the reactivity relationship between potassium and sodium to calcium and magnesium?

Answer 1

K and Na are more reactive than Ca and Mg. K and Na are both alkali metals while Ca and Mg are both alkaline-earth metals.

Alkali metals all have one valence electron in their outer levels. They react quickly to lose that lone valence electron to form cations with a 1+ charge. They react so quickly that they will react with water and give off enough heat to ignite the H2 gas produced.

Alkaline-earth metals all have two valence electrons in their outer levels. They will react to lose these two electrons, but it take them longer to lose two than the alkali metals to lose one. This means their reaction rate is slower than the rate of the alkali metals.