Ion

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In chemistry, a molecule or atom that is electrically charged is called an ion. It is called this because it has a different amount of electrons than it usually has. The process adding or subtracting electrons is called ionization.

Many ions are colourless. Elements in the main groups in the Periodic Table form colourless ions. Some ions are coloured. The transition metal usually form coloured ions.

In physics, atomic nuclei that have been completely ionized are called charged particles. These are ones in alpha radiation.

Ionization happens by applying high energy to atoms. This is done using electrical voltage or by high-energy radiation.

An ionized gas is called plasma.

A simple ion is formed from a single atom.

Polyatomic ions are formed from a group of atoms. Polyatomic ions usually consist of all non-metals atoms, but sometimes the polyatomic ion can have a metalic atom too.

Positive ions are called cations. They are attracted to cathodes (negatively charged electrodes). (Cation is pronounced "cat eye on", not "kay shun".) All simple metal ions are cations.

Negative ions are called anions. They are attracted to anodes (positively charged electrodes). All simple non-metal ions (except H⁺, which is a proton) are anions (except NH₄⁺).

Transition metals can form more than one simple cation with different charges.

Most ions have a charge of less than 4, but some can have higher charges.

Michael Faraday was the first person to write a theory about ions. He did this in 1830. In his theory, he said what the portions of molecules were like that moved to anions or cations. Svante August Arrhenius said how this happened. He wrote this in his doctoral dissertation in 1884. Arrhenius was studying at the University of Uppsala. The university did not accept his theory at first (he only just passed his degree). But in 1903, he won the Nobel Prize in Chemistry in 1903 for the same idea.

In Greek ion is like the word "go". "Anion" and "cation" mean "up-goer" and "down-goer". "Anode" and "cathode" are "way up" and "way down".

[change] Other meanings

In Greek mythology, Ion was a son of Xuthus and Creusa. He founded the Ionian race and became a king of Athens. The term is also used for an element of the Plato texts, and a Window manager.