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Fix Matter see-also invoke

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Fix Matter see-also invoke

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{{Short description|Atom or molecule with a net electric charge}}

{{Quantum matter backlink|Atoms}}

An '''ion''' is an [[Physics:Quantum atoms/atom|atom]] or molecule that has gained or lost one or more [[Physics:Quantum atoms/electron|electrons]], resulting in a net electric charge.<ref>{{cite Collins Dictionary|ion}}</ref>

* A positively charged ion is called a ''cation''.<ref>{{cite Merriam-Webster|cation |access-date=6 October 2021}}</ref>
* A negatively charged ion is called an ''anion''.<ref>{{cite Merriam-Webster|anion |access-date=6 October 2021}}</ref>

Ions play a central role in [[Physics:Quantum Plasma physics|plasma physics]], where matter exists as a collection of free electrons and ions.

[[File:Ionization process.png|thumb|450px|right|Ionization process in which electrons are removed from or added to atoms, producing positively or negatively charged ions.<ref>{{cite Collins Dictionary|ion}}</ref><ref>{{cite Merriam-Webster|cation |access-date=6 October 2021}}</ref><ref>{{cite Merriam-Webster|anion |access-date=6 October 2021}}</ref><ref name="Knoll-1999">{{Cite book |last=Knoll |first=Glenn F. |title=Radiation Detection and Measurement |date=1999 |publisher=Wiley |isbn=978-0-471-07338-3 |edition=3rd |location=New York}}</ref>]]

== Description ==
The charge of an electron is negative by convention, while the charge of a proton is positive. An ion has a nonzero net charge because the number of electrons is not equal to the number of protons.

A cation has fewer electrons than protons, giving it a positive charge. Examples include K+, Na+, and Li+. An anion has more electrons than protons, giving it a negative charge. Examples include Cl−, F−, and OH−.

Ions consisting of one atom are called ''monatomic ions'' or ''atomic ions''. Ions consisting of two or more atoms are called ''polyatomic ions'' or ''molecular ions''.

The net charge of an ion is written as a superscript. For example, Na+ indicates a sodium cation, F− indicates a fluoride anion, and He2+ indicates a doubly charged helium ion.<ref name="ThoughtCo">{{Cite web |title=What Is an Ion? Definition and Examples |url=https://www.thoughtco.com/definition-of-ion-604535 |access-date=26 August 2024 |website=ThoughtCo |language=en |archive-date=26 August 2024 |archive-url=https://web.archive.org/web/20240826143201/https://www.thoughtco.com/definition-of-ion-604535 |url-status=live }}</ref>

== Formation ==
Ions are formed through processes such as:

* ionization, involving loss of electrons
* electron attachment
* electron transfer between atoms or molecules
* collisions in high-energy environments
* dissolution of salts in liquids
* radiation interacting with gases or matter

In physical ionization in a gas or liquid, ion pairs may be created, consisting of a free electron and a positive ion.<ref name="Knoll-1999">{{Cite book |last=Knoll |first=Glenn F. |title=Radiation Detection and Measurement |date=1999 |publisher=[[Wiley (publisher)|Wiley]] |isbn=978-0-471-07338-3 |edition=3rd |location=New York}}</ref>

In chemistry, monatomic ions are commonly formed by the gain or loss of electrons from the valence shell. Sodium, for example, tends to lose one electron:

:<chem>Na -> Na+ + e-</chem>

Chlorine tends to gain one electron:

:<chem>Cl + e- -> Cl-</chem>

The resulting sodium and chloride ions can combine to form sodium chloride:

:<chem>Na+ + Cl- -> NaCl</chem>

== Cations and anions ==
An '''anion''' is an ion with more electrons than protons, giving it a net negative charge.<ref>{{Cite web |last=University of Colorado Boulder |author-link=University of Colorado Boulder |date=21 November 2013 |title=Atoms and Elements, Isotopes and Ions |url=http://ruby.colorado.edu/~smyth/G101-2.html |url-status=live |archive-url=https://web.archive.org/web/20150202061438/http://ruby.colorado.edu/~smyth/G101-2.html |archive-date=2 February 2015 |access-date=22 November 2013 |publisher=colorado.edu}}</ref>

A '''cation''' is an ion with fewer electrons than protons, giving it a net positive charge.<ref>{{Cite web |last1=Douglas W. Haywick, Ph.D. |last2=University of South Alabama |author-link2=University of South Alabama |date=2007–2008 |title=Elemental Chemistry |url=http://www.usouthal.edu/geology/haywick/GY111/111-4.pdf |url-status=live |archive-url=https://web.archive.org/web/20111204134213/http://www.usouthal.edu/geology/haywick/GY111/111-4.pdf |archive-date=4 December 2011 |access-date=22 November 2013 |publisher=usouthal.edu}}</ref>

The words ''anion'' and ''cation'' come from Greek roots connected with motion toward electrodes. They were introduced by [[Biography:Michael Faraday|Michael Faraday]] following consultation with [[Biography:William Whewell|William Whewell]].<ref name="Frank A-1991">{{Cite book |url=https://books.google.com/books?id=9lknVoNGj30C&q=The%20Correspondence%20of%20Michael%20Faraday%20whewell&pg=PA183 |title=The Correspondence of Michael Faraday, Vol. 2: 1832–1840 |year=1991 |isbn=9780863412493 |editor-last=Frank A. J. L. James |page=183 |access-date=16 October 2020 |archive-url=https://web.archive.org/web/20210414164907/https://books.google.com/books?id=9lknVoNGj30C&q=The%20Correspondence%20of%20Michael%20Faraday%20whewell&pg=PA183 |archive-date=14 April 2021 |url-status=live}}</ref>

Because electrons are light and spread out as matter waves, anions are usually larger than their neutral parent atoms, while cations are usually smaller. A hydrogen cation, H+, is essentially a bare proton.

== Ionic bonding ==
Oppositely charged ions attract through electrostatic forces. This attraction can form ionic compounds and crystal lattices. Ionic bonding is especially common between metals, which tend to lose electrons, and nonmetals, which tend to gain electrons.

Ionic compounds contain characteristic distances between neighboring ions, from which ionic radii may be inferred.

== Ionization potential ==
The energy required to remove an electron from an atom or molecule is called the ionization potential or ionization energy. Each successive ionization energy is usually larger than the previous one, especially after a stable shell or subshell has been emptied.

Sodium commonly forms Na+ because it has one valence electron outside a stable inner configuration. Chlorine commonly forms Cl− because it needs one electron to complete a stable valence shell. Caesium has one of the lowest measured ionization energies among the elements, while helium has one of the highest.<ref name="lenntech.com">[http://www.lenntech.com/Periodic-chart-elements/ionization-energy.htm Chemical elements listed by ionization energy] {{Webarchive|url=https://web.archive.org/web/20090330155714/http://www.lenntech.com/Periodic-chart-elements/ionization-energy.htm |date=30 March 2009 }}. Lenntech.com</ref>

== Role in plasma physics ==
In [[Physics:Quantum Plasma physics|plasmas]]:

* ions and electrons move collectively
* long-range electromagnetic forces dominate
* charge neutrality is approximately maintained
* collisions, ionization, and recombination control the plasma state

The behavior of ions is described by [[Physics:Quantum kinetic theory|kinetic theory]] and fluid models such as [[Physics:Quantum Magnetohydrodynamics|magnetohydrodynamics]].

Ions in plasmas can be accelerated, confined, heated, and transported by electric and magnetic fields. Their motion is central to fusion plasmas, astrophysical plasmas, ion beams, and space physics.

== Detection of ionizing radiation ==
The ionizing effect of radiation in gases is widely used for radiation detection. Radiation can create ion pairs, and an applied electric field can collect the charges. The ionization chamber is one of the simplest detectors.<ref name="Knoll-1999" />

Devices such as Geiger–Müller tubes and proportional counters use ionization and electron multiplication to detect alpha particles, beta particles, gamma rays, and X-rays.

== Natural and technological occurrence ==
Ions occur throughout nature. They are important in seawater, biological systems, atmospheric chemistry, the ionosphere, plasmas, and stellar environments.

Ions are also used in technology, including:

* mass spectrometers
* particle accelerators
* ion sources
* ion implantation
* ion engines
* optical emission spectrometers
* air ionisers
* radiation detectors

In biological systems, ion gradients across cell membranes are essential for signaling, metabolism, and cell function.

== History ==
The word ''ion'' was introduced by [[Biography:Michael Faraday|Michael Faraday]] in 1834 for charged species that move through an aqueous medium between electrodes.<ref>{{Cite AV media |url=https://www.bbc.co.uk/history/historic_figures/faraday_michael.shtml |title=Michael Faraday (1791–1867) |publisher=[[BBC]] |place=UK |access-date=21 December 2019 |archive-date=25 August 2016 |archive-url=https://web.archive.org/web/20160825051236/http://www.bbc.co.uk/history/historic_figures/faraday_michael.shtml |url-status=live }}</ref><ref>{{Cite web |title=Online etymology dictionary |url=http://www.etymonline.com/index.php?term=ion |url-status=live |archive-url=https://web.archive.org/web/20110514084635/http://www.etymonline.com/index.php?term=ion |archive-date=14 May 2011 |access-date=7 January 2011}}</ref>

In 1884, [[Biography:Svante Arrhenius|Svante Arrhenius]] explained that crystalline salts dissociate into charged particles when dissolved. This work contributed to his 1903 Nobel Prize in Chemistry.<ref>{{Cite web |title=The Nobel Prize in Chemistry 1903 |url=https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1903/index.html |url-status=live |archive-url=https://web.archive.org/web/20180708044958/https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1903/index.html |archive-date=8 July 2018 |access-date=13 June 2017 |website=nobelprize.org}}</ref><ref name="Columbia University-1976">{{Cite book |url=https://archive.org/details/newcolumbiaencyc00harr/page/155 |title=The New Columbia Encyclopedia |date=1976 |publisher=[[Columbia University]] |isbn=978-0-231-03572-9 |editor-last=Harris |editor-first=William |edition=4th |location=New York City |page=[https://archive.org/details/newcolumbiaencyc00harr/page/155 155] |editor-last2=Levey |editor-first2=Judith}}</ref><ref name="EncBrit">{{Cite book |last=Goetz |first=Philip W. |title=The New Encyclopædia Britannica |date=1992 |work=Chicago: Encyclopaedia Britannica Inc |publisher=[[Encyclopædia Britannica, Inc.]] |isbn=978-0-85229-553-3 |editor-last=McHenry |editor-first=Charles |edition=15 |volume=1 |location=Chicago |page=587 |bibcode=1991neb..book.....G}}</ref><ref name="SciBio">{{Cite book |title=Dictionary of Scientific Biography |date=1970 |publisher=[[Charles Scribner's Sons]] |isbn=978-0-684-10112-5 |editor-last=Cillispie |editor-first=Charles |edition=1 |location=New York City |pages=296–302}}</ref>

== Physical interpretation ==
An ion represents a deviation from electrical neutrality at the atomic or molecular level. Its dynamics are governed by electromagnetic forces and play a fundamental role in plasma physics, chemistry, condensed matter physics, radiation detection, and biological systems.

== Properties ==

* atom or molecule with nonzero electric charge
* formed by gaining or losing electrons
* may be positive or negative
* strongly affected by electric and magnetic fields
* participates in ionic bonding and plasma behavior
* central to ionization, spectroscopy, and radiation detection

=See also=
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also/Matter}}

=References=
{{reflist|3}}

{{Author|Harold Foppele}}

{{Sourceattribution|Ion|1}}

Physics:Quantum atoms/ion - Revision history

imported>WikiHarold: Fix Matter see-also invoke

imported>WikiHarold: Fix Matter see-also invoke