Refer to the illustration of the periodic table to determine which formula is correct.
Mg3O2
Mg2O
MgO2
MgO

D. MgO

Explanation:

We need to look at the charge of element. (Look at a periodic table for this)

Mg, which is Magnesium, has a charge of 2+ because it's in the second column, or group, from the left.

O, which is Oxygen, has a charge of 2- because it's in the second column, or group, from the right.

Since Mg is 2+, it's the cation and since O is 2-, it's the anion. We can put these two elements together into an ionic compound.

Mg^(2+) and O^(2-) becomes Mg2O2, where we can cancel the 2s: MgO.

Thus, the answer is D.

Hope this helps!