Meaning & use
ion
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Meaning
nouncountablephysicschemistry
An atom or molecule with an electric charge because it has gained or lost electrons.
Grammar: Regular countable noun; plural ions. Positive ions have lost electrons and negative ions have gained them.
Patterns
- positive or negative ion
- form ions
- ion channel
Table salt dissolves in water and releases sodium and chloride ions.
A calcium ion helps trigger the muscle response.
The battery moves lithium ions between two electrodes.
Word forms
| plural | ions |
|---|
Common combinations
- positive ion
- A positive ion has fewer electrons than protons.
- negative ion
- A negative ion gains one or more extra electrons.
- ion channel
- Each ion channel lets only certain charged particles pass.
- sodium ion
- The pump moves a sodium ion out of the cell.
Synonyms and how they differ
- charged particle
- Charged particle is broader and can include subatomic particles; ion specifically means an atom or molecule with charge.
- electrolyte
- An electrolyte is a substance that makes ions in solution; the ion is the charged particle itself.
- cation
- A cation is only a positively charged ion, not every ion.
- anion
- An anion is only a negatively charged ion, not every ion.
Opposites
Word family
- ionic adjective
- Relating to ions or bonds formed by ion transfer.
- ionize verb
- To convert atoms or molecules into ions.
- ionization noun
- The process of forming ions.
Commonly confused: ion or iron?
ion vs iron
Iron is a metal element; ion is a charged atom or molecule and is pronounced differently.
Practice
An ion forms when an atom or molecule ___.
Choose one answer.
Ions are created by electron transfer, which changes the electric charge while the nucleus stays essentially the same. Losing protons would change the element, neutrality is the opposite state, and basalt is an unrelated rock.
Make it your own
Write a sentence using “ion”, then check it and compare it with the examples above.