All of the alkaline earth metals are similar in that – they are all artificially made elements they all have similar atomic weights. they all have the same ionic charge. they all show variable valences.

they all have the same ionic charge.

Explanation:

Alkaline earth metals are group 2 metals on the periodic table. They are divalent elements because they have two valence electrons and ionize by donating these two valence electrons. Elements in this group have the same numbers of electrons in their outermost shell of their atoms. i.e. they all have the same number of valence electrons and ionic charge.