Answer: Magnesium atom looses 2 electrons to obtain the noble gas structure.
Explanation:
Atomic number of magnesium is 12. Electronic configuration of magnesium :
\([Mg]=1s^22s^22p^63s^2\)
In the periodic table, the nearest noble gas to magnesium element is Neon with atomic number 10.
\([Ne]=1s^22s^22p^6\)
So, in order to obtain noble gas electronic configuration the magnesium atom will loose 2 electrons.
\([Mg^{2+}]=1s^22s^22p^6\)
