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!

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.