Lewis Acids

The Lewis theory of acid-base reactions describes Lewis acids and bases as electron pair acceptors and donors, respectively. In order to create a product with a coordinate covalent bond, a Lewis base can give a pair of electrons to a Lewis acid. A Lewis adduct is another name for this item. Chemical compounds known as Lewis Acids contain vacant orbitals and can take electron pairs from Lewis Bases. This phrase was historically used to refer to chemical species that had an empty p-orbital and a trigonal planar structure. Such a Lewis acid would be BR3, for instance. Since water and some other substances can accept and donate electron pairs based on the Lewis model, they are regarded as both Lewis acids and bases. Lewis acids that may receive electron pairs are frequently seen in the following examples:

In addition to onium ions like H3O+, H+ ions (or protons) can be regarded as Lewis acids.

High oxidation state cations from d-block elements can serve as acceptors for an electron pair. Fe3+ is an illustration of one of these cations.

Water serves as the ligand in coordination compounds that are formed by metal cations like Mg2+ and Li+. These aquo compounds feature Lewis acid behaviour and the ability to receive electron pairs.
H3C+ and other trigonal planar compounds are known to produce carbocations that are more likely to receive electron pairs. Group 15 elements Antimony, Arsenic, and Phosphorus all have pentahalides that can function as Lewis acids.