The element M is most likely to belong to Group 2 of the Periodic Table. This group is also known as the alkaline earth metals. The elements in this group all have two valence electrons, which they readily lose to form stable +2 ions. This means that their chlorides all have the formula MCl2. The elements in Group 2 are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).