* Lewis Acids: Accept electron pairs.

* Lewis Bases: Donate electron pairs.

AlCl3's Structure:

* Aluminum has three valence electrons.

* Chlorine has seven valence electrons.

* In AlCl3, aluminum forms three covalent bonds with chlorine atoms.

* This leaves the aluminum atom with an incomplete octet, making it electron-deficient.

Why AlCl3 is a Lewis Acid:

The electron-deficient aluminum atom in AlCl3 readily accepts an electron pair from a donor molecule, making it a Lewis acid. This is often seen in reactions where AlCl3 acts as a catalyst. For example, it is used in Friedel-Crafts alkylation and acylation reactions.