Ion

An ion is a particle with a net positive or negative charge. Ions may be formed from single atoms ("monatomic ions") or from molecules ("molecular ions" or "complex ions"). An atom or molecule can become charged when it either gains or loses an electron so that the number of electrons and protons in the nucleus are no longer equal. Ions that have at least one 'extra' electron are negatively charged, and are called anions. Ions that have lost at least one electron are positively charged, and are called cations.

Ions are very chemically reactive (they easily undergo chemical reactions), which can cause problems in biological systems. There are a number of ways to produce ions: some chemical reactions (combustion for example) will produce ionic products, and ionic compounds (like salt) will dissociate in water to release ions into solution. Additionally, if radiation with enough energy hits an atom or molecule, it can eject an electron from the atom or molecule, creating a cation. High-energy radiation capable of creating ions from neutral atoms or molecules is collectively called ionizing radiation.

To learn more about ions please see the chemistry LibreText.

Phet: Build an Atom

Below is a interactive PhET simulation from the University of Colorado. This simulation creates an atom from protons, neutrons and electrons and test skills with the periodic table.

For Further Reading

• Atom
• Electric charge
• Ionization
• Ionizing radiation
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