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
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. An is a negatively charged ion formed when
: 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). According to the octet rule , atoms often
: When an atom gains an electron, it becomes an anion. : When an atom gains an electron, it becomes an anion
: 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