* Lewis Acids: Accept electron pairs.

* Lewis Bases: Donate electron pairs.

Mg²⁺ has a positive charge, meaning it has lost two electrons. This leaves it with an empty orbital that can readily accept an electron pair.

Example: In the reaction of Mg²⁺ with water, Mg²⁺ acts as a Lewis acid by accepting an electron pair from the lone pair on the oxygen atom of water.

Therefore, due to its electron-deficient nature, Mg²⁺ is classified as a Lewis acid.