* Electronegativity Difference: Magnesium (Mg) is a metal with a low electronegativity, while oxygen (O) is a nonmetal with a high electronegativity. This significant difference in electronegativity (about 2.1) leads to the transfer of electrons, a characteristic of ionic bonding.

* Formation of Ions: Magnesium readily loses two electrons to achieve a stable octet, becoming a positively charged magnesium ion (Mg²⁺). Oxygen gains two electrons to complete its octet, forming a negatively charged oxide ion (O²⁻).

* Electrostatic Attraction: The oppositely charged ions attract each other strongly through electrostatic forces, creating a strong ionic bond.

In summary, MgO is formed by the electrostatic attraction between positively charged magnesium ions and negatively charged oxide ions, making it an ionic compound.