What allows ammonia to act as a Lewis base in water?

• A. Its planar structure
• B. Its capacity to act as an oxidizing agent
• C. The donation of an electron pair
• D. Its acidic properties in solution

Answer: (C)

Ammonia acts as a Lewis base in water primarily due to its ability to donate a pair of electrons. In Lewis theory, a Lewis base is defined as a substance that can donate an electron pair to form a covalent bond. Ammonia (NH₃) has a nitrogen atom with a lone pair of electrons, which it can readily donate to a Lewis acid, facilitating the formation of a new bond.

When ammonia is placed in water, it can interact with protons (H⁺) from the water molecules, accepting them to form ammonium ions (NH₄⁺). This electron pair donation is a key characteristic of Lewis bases, distinguishing them from other concepts such as acidity or structural properties. In this context, ammonia does not function as an oxidizing agent nor is it planar; rather, its effectiveness as a Lewis base hinges on its ability to use its lone pair of electrons to interact with other species in solution.