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Cation: Definition & Examples

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Instructor: Elizabeth (Nikki) Wyman

Nikki has a master's degree in teaching chemistry and has taught high school chemistry, biology and astronomy.

Ions are elements which have a charge, the positively charged form of which is known as a cation. Understand the definition and explore how cations are formed and behave through examples of both metal and non-metal elements. Updated: 09/23/2021

What Is a Cation?

When a single element or group of elements has a charge, it is known as an ion. When an ion is positively charged, it's called a cation.

When an element or compound is in cation form, it can be represented by either the element symbol or by a compound formula, with the amount of charge written as a superscript immediately after the symbol or formula, as seen in the following table:

Name of Cation and Charge Symbol of Cation
Potassium, +1 K+
Calcium, +2 Ca2+
Vanadium, +4 V4+

An easy way to remember that cations are positive ions is by replacing the 't' in 'cation' with a positive sign, +. Instead of writing cation, you would write ca+ion. The positive sign bears enough likeness to a 't' to be read as cation, yet it reminds you of the definition!

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  • 0:00 What Is a Cation?
  • 0:35 How a Cation Forms
  • 1:30 Examples of Cations
  • 2:25 Cations in Action
  • 3:50 Lesson Summary
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How a Cation Forms

Cations form when an element or group of elements (compounds) lose one or more electrons. For many people, this idea is somewhat counterintuitive because we do not equate losing things with being positive. But electrons are actually negatively charged particles. So, when an element loses an electron, it becomes less negative and more positive.

The sodium atom loses one electron to become a +1 cation. The process is shown in the following diagram:

In figure one, the sodium atom has 11 electrons. When sodium loses one electron, it becomes a +1 cation as shown in figure two. The +1 sodium cation now has 10 electrons, so it is smaller in size than when it had 11 electrons.

Examples of Cations

Cations can be formed from metal elements, as well as nonmetal elements. If a metal element forms an ion, it always forms a cation. Some metals always form the same type of cation. For example, sodium always forms a +1 cation and magnesium always forms a +2 cation. Some metals are flexible and can form more than one type of cation. Copper can form +1 or +2 cations, and iron can form +2 or +3 cations.

Nonmetal elements, like nitrogen, oxygen, and hydrogen, are capable of forming cations as well. Hydrogen occurs quite frequently as a +1 cation, while nitrogen and oxygen can form cations when they are in compound form. The ammonium ion is a type of cation formed when nitrogen is bonded to four hydrogens. Examples of nonmetal cations are shown in the following table:

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