What is a Lewis acid defined as?

A Lewis acid is defined as a substance that accepts electrons. This definition stems from the broader concept of acid-base chemistry developed by Gilbert Lewis. According to Lewis theory, an acid is any species that can accept an electron pair from a donor, which is labeled as a Lewis base. This acceptance of electron pairs allows Lewis acids to interact with many different types of substances, making this definition quite versatile.

In contrast, the other definitions provided in the question refer to other types of chemical behavior. For instance, substances that produce hydroxide ions are typically classified as Brønsted-Lowry bases, while those that donate protons are clearly Brønsted-Lowry acids. The production of hydrogen ions is specifically associated with the behavior of acids in aqueous solutions and does not encompass the broader definition established by the Lewis theory. Therefore, identifying the Lewis acid as an electron acceptor accurately aligns with the definitions and principles of acid-base chemistry as put forth by Lewis.