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+