In terms of Lewis theory, what is a Lewis acid?

In Lewis theory, a Lewis acid is defined as an electron pair acceptor. This means that a Lewis acid can accept a pair of electrons from a Lewis base during a chemical reaction. This interaction forms a coordinate covalent bond, where the Lewis base donates its electrons to the Lewis acid.

For instance, in a reaction between a Lewis acid and a Lewis base, the electron-deficient species, often metal ions or molecules with an incomplete octet, can readily accept electron pairs to achieve a more stable electronic configuration. An example of a Lewis acid would be aluminum chloride, which can accept an electron pair from a Lewis base such as ammonia.

In contrast, the other options refer to concepts that do not align with the definition of a Lewis acid. Lone pair donors correspond to Lewis bases, while hydrogen ion donors and proton donors refer to Bronsted acids rather than Lewis acids. This distinction is crucial for accurately identifying and understanding different types of acids in acid-base chemistry.