Cation Definition and Examples

The hydronium cation is the simplest type of oxonium ion.
The hydronium cation is the simplest type of oxonium ion. Jacek FH, Wikipedia Commons
By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on May 05, 2019

A cation is an ionic species with a positive charge. The word "cation" comes from the Greek word "kato," which means "down." A cation has more protons than electrons, giving it a net positive charge.

Cations with multiple charges may be given special names. For example, a cation with a +2 charge is a dication. One with a +3 charge is a trication. A zwitterion has both positive and negative charges at different regions of the molecule, yet an overall neutral charge.

The symbol for a cation is the element symbol or molecular formula, followed by a superscript of the charge. The number of the charge is given first, followed by a plus symbol. If the charge is one, the numeral is omitted.

Examples of Cations

Cations may be either ions of atoms or of molecules. Examples include:

  • Ag+
  • Al3+
  • Ba2+
  • Ca2+
  • H+
  • H3O+
  • Li+
  • Mg2+
  • NH4+
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Helmenstine, Anne Marie, Ph.D. "Cation Definition and Examples." ThoughtCo, Aug. 25, 2020, thoughtco.com/cation-definition-and-examples-602142. Helmenstine, Anne Marie, Ph.D. (2020, August 25). Cation Definition and Examples. Retrieved from https://www.thoughtco.com/cation-definition-and-examples-602142 Helmenstine, Anne Marie, Ph.D. "Cation Definition and Examples." ThoughtCo. https://www.thoughtco.com/cation-definition-and-examples-602142 (accessed April 25, 2024).