In the Lewis definition, what is the role of an acid?

In the Lewis definition of acids and bases, a Lewis acid is defined as a species that accepts a pair of electrons. This definition expands the traditional view of acids and bases beyond just protons and hydroxide ions, as described in Brønsted-Lowry theory.

The role of a Lewis acid is centered around its ability to form a coordinate covalent bond with a Lewis base, which donates a pair of electrons. In this interaction, the Lewis acid will have an empty orbital or be in a state where it can accommodate additional electrons, facilitating the donation of electrons from the base. This is why the correct answer is the option that describes the Lewis acid's role as an electron pair acceptor.

Understanding this concept allows students to grasp the broader interactions in chemistry, particularly those involving transition metals and complex ions, where electron pair acceptance is crucial to various reactions and bonding scenarios.