Here's why:

* Alkaline earth metals are found in Group 2 of the periodic table. They are characterized by having two valence electrons. Examples include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

* Aluminum is located in Group 13 of the periodic table. It has three valence electrons.

Therefore, aluminum belongs to a different group in the periodic table and has different chemical properties than alkaline earth metals.