Which of the following is not the correct statement?

The correct answer A proton is a Lewis base.

Concept:-

• Lewis Acid and Base: According to Lewis theory, an acid is a substance that can accept an electron pair, while a base is a substance that can donate an electron pair.
• Hydroxyl Ion: Hydroxyl ion (OH^-) has a pair of electrons that can be donated to form a bond. Therefore, according to Lewis theory, it is a base.
• Boron Trichloride: BCl₃ is a molecule that can accept an electron pair due to having an empty orbital. Thus, it can act as a Lewis acid.

Explanation:-

Considering the Lewis acid-base theory, let's evaluate each statement:

• Hydroxyl ion is a Lewis base: This is correct. The hydroxyl ion (OH^-) has an extra pair of electrons that it can donate, and so it qualifies as a Lewis base.
• BCl₃ acts as a Lewis acid: This is also correct. Boron in BCl₃ has an empty orbital and can accept an electron pair, so BCl3 is a Lewis acid.
• A proton is a Lewis base: This is incorrect. A proton (H⁺) is in fact a Lewis acid, not a base. It is deficient of electrons and can accept an electron pair.

In conclusion, the third statement is incorrect, making the answer option 3) A proton is a Lewis base.