Which of the following is the correct definition of a Lewis acid?

• A. A substance that accepts a proton ($H^{+}$) in a chemical reaction.
• B. A substance that accepts an electron pair in a chemical reaction.
• C. A substance that donates an electron pair in a chemical reaction.
• D. A substance that donates a proton ($H^{+}$) in a chemical reaction.

Answer: (B)

Verified step by step guidance

1. Identify the concept of Lewis acids and bases. A Lewis acid is defined as a substance that can accept an electron pair, while a Lewis base is a substance that can donate an electron pair.
2. Review the options provided in the problem. The options describe different types of acids and bases, including those that involve protons (H+).
3. Recognize that the definition involving the acceptance of an electron pair corresponds to the concept of a Lewis acid.
4. Differentiate between the Lewis and Brønsted-Lowry definitions. A Brønsted-Lowry acid is one that donates a proton (H+), which is different from the Lewis definition.
5. Conclude that the correct definition of a Lewis acid is 'A substance that accepts an electron pair in a chemical reaction,' as it aligns with the Lewis theory of acids and bases.