Question

Why are neither the alkali metals nor the alkaline-earth metals found uncombined in nature?

Answer 1

The alkali and alkaline earth metals are rarely found unreacted because they are so reactive.

Explanation:

Sodium `Na_11^23` is so reactive that if sodium metal is placed in water it will react vigorously to produce Hydrogen gas and heat often causing an explosion.

All of the IA group elements ( Alkali metals) have only one valance electron. `s^1`This electron is very unstable. If Alkali metals lose that `s^1` , the Alkali metals will have the electron configuration of a noble gas group VIIIA the most stable of all elements.

So losing electrons will make sodium more stable so this is what all the Alkali Metals tend to do. Because of this the electro negativity of the Alkali Metals is the lowest of any group of elements.

The same is basically true of the group II A alkaline earth metals.
The Alkaline earth metals have 2 s electrons `s^2` . Like the IA group of I A metals the IIA group is much more stable if it loses both electrons.