What is a base defined as in chemistry?

In chemistry, a base is defined as a proton acceptor. This concept comes from the Brønsted-Lowry theory of acids and bases, which posits that acids are substances that can donate protons (H⁺ ions), while bases are substances that can accept those protons. When a base interacts with an acid, it accepts a proton to form a conjugate acid.

For example, when ammonia (NH₃) acts as a base, it accepts a proton from water (H₂O) to form ammonium (NH₄⁺) and hydroxide ions (OH⁻). This ability to accept protons is a fundamental characteristic of bases according to this theory, distinguishing them from acids, which are defined by their ability to donate protons.

Understanding this classification is crucial in various chemical reactions, including neutralization reactions, where an acid and a base react to form water and a salt. The interaction between protons and bases is central to many chemical processes in both organic and inorganic chemistry.