Carboxylate anions are negatively charged ions formed from carboxylic acids when they lose a hydrogen ion (H⁺). They contain a carboxyl group, which is represented as -COO⁻. This group consists of a carbon atom double-bonded to an oxygen atom and single-bonded to another oxygen atom, which carries the negative charge. These anions play a significant role in various chemical reactions and biological processes. They are commonly found in organic compounds and are important in the formation of salts, such as sodium acetate, where the carboxylate anion is paired with a positive ion like Na⁺.