Alkaline earth metals have two valence electrons. This group of elements is located in group 2 of the periodic table, which includes beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
The reason these elements have two valence electrons is that they each possess two electrons in their outermost shell. This configuration makes them more reactive than the noble gases, which have full outer shells. Alkaline earth metals tend to lose these two electrons easily, forming cations with a +2 charge, which is a key characteristic of their chemistry.