Cation
Definition and meaning of Cation in chemistry.
A cation is an ion that carries a net positive electric charge, formed when a neutral atom or molecule loses one or more electrons. Because it has more protons than electrons, a cation is attracted toward the cathode (negative electrode) in electrolysis, which is how it got its name.
In more detail
Cations form most readily from metals and other elements with low ionization energy, since removing electrons from these atoms requires relatively little energy. The resulting ion is smaller than its parent atom because losing electrons reduces electron-electron repulsion and often removes an entire outer shell, letting the remaining electrons draw closer to the nucleus. Cations are essential to ionic bonding, where they are held to anions by electrostatic (Coulombic) attraction, and to countless biological processes, such as nerve signaling driven by sodium and potassium cations crossing cell membranes.
Key facts
| Charge | Positive (net) |
|---|---|
| Formed by | Loss of one or more electrons from a neutral atom or molecule |
| Common example | Na+ (sodium cation) |
| Field | General Chemistry |
Sodium metal (Na) readily loses one electron to form the sodium cation Na+, which combines with the chloride anion Cl- to form the ionic compound sodium chloride (table salt).
Frequently asked questions
Why is it called a cation?
The name comes from the Greek 'kation' (going down), coined by Michael Faraday because these positive ions migrate toward the cathode, the negatively charged electrode, during electrolysis.
Is a cation bigger or smaller than its neutral atom?
Smaller. Removing an electron decreases electron-electron repulsion and can eliminate an entire electron shell, allowing the remaining electrons to be pulled closer to the nucleus.