What is an anion?

An anion is defined as an ion that has gained one or more electrons, resulting in a net negative charge. When an atom acquires extra electrons, the number of negatively charged electrons exceeds the number of positively charged protons in the nucleus, leading to an overall negative charge. This charge imbalance is what characterizes an anion.

The process of electron gain occurs in atoms that typically have a tendency to gain electrons to achieve a more stable electron configuration, often in accordance with the octet rule. Common examples of anions include chloride (Cl⁻), which forms when a chlorine atom gains an electron, and oxide (O²⁻), which arises when an oxygen atom gains two electrons.

In contrast, an atom that has lost electrons would become a positively charged ion, known as a cation. A neutral atom is one with equal numbers of protons and electrons, thus not exhibiting any charge. Finally, the process of forming a covalent bond involves sharing electrons between atoms, which does not directly relate to the definition of anions.