Answer:
When Magnesium reacts with Oxygen,
Magnesium gives up 2 electrons and oxygen takes those 2 electron. In this way they form an ionic bond and their outer shell also become full of electrons.
Now, The ions: Magnesium ion is Mg^2+ and Oxygen ion is O^2-
Note that the ions are opposite charged. As we know, opposite charges attract, they form a lattice where the ions are bonded with a strong ionic bond.
