When all group IIA elements (alkaline earth metals) lose their two valence electrons, their remaining electron configurations become the same as those of the group VIIIA elements (noble gases).

Here's why:

* Group IIA elements have two electrons in their outermost shell (s-orbital).

* Group VIIIA elements have a full outer shell, making them very stable.

* When group IIA elements lose their two valence electrons, they achieve the same electron configuration as the noble gas in the previous period.

For example:

* Magnesium (Mg) (Group IIA) loses its two valence electrons to become Mg²⁺. Its remaining electron configuration is [Ne] 2s²2p⁶, which is the same as Neon (Ne) (Group VIIIA).

* Calcium (Ca) (Group IIA) loses its two valence electrons to become Ca²⁺. Its remaining electron configuration is [Ar] 3s²3p⁶, which is the same as Argon (Ar) (Group VIIIA).

This is why alkaline earth metals readily form +2 cations and are highly reactive, striving to achieve the stable electron configuration of the noble gases.