Which of the following describes an anion?

An anion is defined as a negatively charged ion that has gained one or more electrons, resulting in an excess of negative charge. This process typically occurs when an atom or molecule acquires additional electrons, which can happen during chemical reactions or interactions. For instance, when a chlorine atom gains an electron, it becomes a chloride ion, represented as Cl^-. This gained electron increases the overall charge of the atom, turning it into an anion.

In contrast, positively charged ions, known as cations, result from the loss of electrons and are not classified as anions. Atoms that share electrons are typically involved in covalent bonding and do not reflect the characteristics of anions. Additionally, the donation of protons relates to acids and bases, governed by the Brønsted-Lowry theory, which is distinct from the behavior of anions in relation to charge. Thus, the description of an anion as a negatively charged ion accurately aligns with its definition in the context of chemistry.