NO2 (nitrogen dioxide) is classified as a Lewis acid. A Lewis acid is a substance that can accept an electron pair. In the case of NO2, the nitrogen atom has a vacant orbital that can accept an electron pair from a Lewis base.
Here’s a more detailed explanation:
- NO2 has a nitrogen atom with a +1 formal charge, which means it is electron-deficient.
- The nitrogen atom in NO2 has an empty p-orbital that can accept an electron pair.
- When NO2 interacts with a Lewis base, the base donates an electron pair to the nitrogen atom, forming a coordinate covalent bond.
Therefore, NO2 acts as a Lewis acid because it can accept an electron pair from a Lewis base.