What is the term used for a negatively charged ion?

The term for a negatively charged ion is "anion." Anions form when atoms gain one or more electrons, resulting in a net negative charge. This gain of electrons is typically a response to the need for the atom to achieve a more stable electron configuration, often aligning with the octet rule, where atoms strive to have eight electrons in their outer shell.

Cations refer to positively charged ions that occur when an atom loses electrons. A neutral ion is not a standard term used in chemistry, as ions, by definition, are charged species. Polyatomic ions are groups of atoms that carry a charge due to a surplus or deficit of electrons, but they can also be anions or cations. Therefore, the distinction of an anion as specifically referring to a negatively charged ion is clear and precise.