Final answer:
The identity of element Q is magnesium (Mg), as its ion Q2+ with 10 electrons signifies that the neutral atom would have 12 electrons, corresponding to magnesium's position on the periodic table in group 2.
Step-by-step explanation:
The identity of element Q can be determined based on the number of electrons in its ion Q2+. An ion with a 2+ charge has lost two electrons. Therefore, the neutral atom of element Q would have 12 electrons, because the ion Q2+ has 10 electrons (12-2=10). The element with 12 electrons in its neutral state is magnesium (Mg), which is located in group 2 of the periodic table. This falls in line with the fact that magnesium typically forms a 2+ ion when it loses two electrons to attain a stable noble gas electron configuration.