Here's why:

* Magnesium (Mg) is in Group 2 of the periodic table, meaning it has 2 valence electrons (electrons in the outermost shell).

* To achieve a stable electron configuration, magnesium wants to lose these 2 valence electrons.

* Losing 2 negatively charged electrons leaves the magnesium atom with a +2 charge.

Therefore, the ionic form of magnesium is Mg²⁺.