* The Lone Pair: Ammonia has a lone pair of electrons on the nitrogen atom. This lone pair is highly reactive and seeks a positive charge to bond with.
* Proton Acceptor: When ammonia encounters a proton (H⁺), the lone pair on the nitrogen atom readily accepts the proton, forming the ammonium ion (NH₄⁺). This is the defining characteristic of a base – it accepts protons.
* Brønsted-Lowry Theory: The Brønsted-Lowry theory of acids and bases defines a base as a proton acceptor. Ammonia fulfills this definition by reacting with acids to form the ammonium ion.
* Equilibrium: Ammonia's reaction with water is a good example of its basic nature. In solution, ammonia reacts with water to form ammonium ions (NH₄⁺) and hydroxide ions (OH⁻), increasing the hydroxide concentration and making the solution alkaline:
NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH⁻(aq)
In summary: Ammonia is considered a base because it has a lone pair of electrons that readily accepts protons, fulfilling the definition of a base according to the Brønsted-Lowry theory. This is evident in its reaction with water, which results in an increase in hydroxide ion concentration and alkaline properties.
