Final answer:
The correct representation of magnesium oxide (MgO) as an ionic compound is by showing magnesium as a cation with a 2+ charge and oxygen as an anion with a 2- charge, forming Mg2+O2- or simply MgO.
Step-by-step explanation:
The correct way to represent the ionic compound magnesium oxide (MgO) is that magnesium (Mg) becomes a cation with a 2+ charge (Mg2+), and oxygen (O) becomes an anion with a 2- charge (O2-). In the dot structure, magnesium would not be surrounded by valence electrons since it loses its two valence electrons, and oxygen would have a total of eight valence electrons, showing a complete outer shell or octet. Thus, the ionic bonding is due to the attractions between Mg2+ and O2-, forming MgO where these charges balance out and no square brackets are needed as the compound does not exist as discrete molecules.