Definition - What does Ion mean?

An ion is an atom (or group of atoms) that has gained or lost one or more electrons and has become electrically charged. There are two types of ions: anions and cations.

Ions are responsible for diverse phenomena, from the luminescence of the Sun to the existence of the Earth's ionosphere. It is very important in terms of corrosion because ionic exchange is a very common corrosion mechanism.

As reactive charged particles, they are also used in air purification by disrupting microbes, and in household items such as smoke detectors.

Corrosionpedia explains Ion

An ion is an atom that carries an electrical charge. Ions can be created by either chemical or physical means. If a neutral atom loses one or more electrons, it becomes positively charge and is known as a cation. If an atom gains electrons, it becomes negatively charged and is known as an anion. For example, when sodium (Na) loses an electron and chlorine (Cl) gains an electron, then:

The Na becomes a cation, Na+.

The Cl becomes a anion, Cl-.

When writing the chemical formula for an ion, its net charge is written in superscript immediately after the chemical structure for the molecule/atom.

An ion consisting of a single atom is an atomic or monatomic ion; if it consists of two or more atoms, it is a molecular or polyatomic ion.

In the case of physical ionization of a medium, such as a gas, what are known as "ion pairs" are created by ion impact, and each pair consists of a free electron and a positive ion.

Ions in their gas-like state are highly reactive, and do not occur naturally in large quantities on Earth, except in flames, lightning, electrical sparks and other plasmas. These gas-like ions rapidly interact with ions of opposite charge to produce neutral molecules or ionic salts. Ions are also produced in the liquid or solid state when salts interact with solvents (such as water) to produce solvated ions, which are more stable.

If an ion contains unpaired electrons, it is called a radical ion, it is very reactive. Polyatomic ions containing oxygen, such as carbonate and sulfate, are called oxyanions. Molecular ions that contain at least one carbon-to-hydrogen bond are called organic ions.

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