Anions exist in various forms, from simple atoms to complex molecular groups: Cation vs Anion: Definitions & Periodic Table Guide

: When an atom gains an electron, it becomes an anion.

Anions are typically formed by . According to the octet rule , atoms often gain electrons until their outermost shell is full, typically containing eight electrons. This process is driven by the atom's electronegativity—its ability to attract and hold onto electrons.

: The number of electrons gained is indicated by a superscript after the chemical symbol (e.g., Cl−cap C l raised to the negative power for a gain of one electron, O2−cap O raised to the 2 minus power for a gain of two).

An is a negatively charged ion formed when an atom or molecule gains one or more electrons. This surplus of electrons relative to protons gives the particle a net negative charge, a fundamental concept in chemistry that governs how matter bonds and reacts. The Basics of Anion Formation

: In simple monoatomic anions, the ending of the element's name is typically replaced with "-ide". For example, chlorine becomes chloride ( Cl−cap C l raised to the negative power ) and oxygen becomes oxide ( O2−cap O raised to the 2 minus power Common Examples