What characterizes an acid in chemical terms?

An acid is characterized in chemical terms as a source of hydrogen ions, denoted as H⁺. This definition is fundamental to the Brønsted-Lowry theory of acids and bases, which emphasizes that an acid is a substance that can donate a proton (H⁺) to a base during a chemical reaction.

When an acid dissolves in water, it increases the concentration of hydrogen ions in the solution, which can lead to various observable properties, such as a sour taste, the ability to conduct electricity, and the ability to react with bases to form salts and water. The production of hydrogen ions is crucial for identifying a substance as an acid, and it underpins many acid-base reactions.

The other options refer to different types of ions that do not define an acid. Oxygen ions and hydroxide ions are associated with bases, while carbonate ions relate to specific reactions with acids but do not characterize them. Thus, the identification of an acid fundamentally revolves around its ability to release H⁺ ions into a solution.