Polyatomic Ion Definition and Examples

What Is a Polyatomic Ion in Chemistry?

This is the chemical structure of the pyrophosphate anion, an example of a polyatomic ion.
This is the chemical structure of the pyrophosphate anion, an example of a polyatomic ion. Todd Helmenstine
by Anne Marie Helmenstine, Ph.D.
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.
Updated March 06, 2017

Polyatomic Ion Definition

A polyatomic ion is an ion comprised of two or more atoms.

Examples: The hydroxide cation (OH-) and the phosphate cation (PO43-) are both polyatomic ions.