A positively charged ion refers to an atom that has lost electrons, each electron lost will equal a positive charge. In this case, a +2 ion means that the atom has lost 2 electrons.
The electrons that an atom loses are those that are in the last energy level, that is, the valence electrons. It will be easier to lose two electrons if in the last level the atom has only two valence electrons. So the element that will lose electrons more easily will be the one that is in group II of the periodic table.
Remember that the group represents the valence electrons, so if it is in group II it will have two valence electrons. The element found in group II of the periodic table is calcium, therefore calcium will have two valence electrons that it can easily lose, leaving the Ca+2 ion as a result.
So, the answer is calcium