Science
What is an Ion?
An ion is an atom or molecule that has gained or lost one or more electrons, giving it an electric charge. Losing electrons makes a positive ion; gaining them makes a negative ion. Ions are behind everything from table salt to the electrical signals in your nerves.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains an ion.
Key things to understand
- 1An atom is normally neutral (equal protons and electrons); an ion has lost or gained electrons, so it's charged.
- 2Lose electrons → positive ion (cation); gain electrons → negative ion (anion).
- 3Oppositely charged ions attract and can bond — sodium and chloride ions form table salt (NaCl).
- 4Ions let solutions conduct electricity, which is why salty water conducts.
- 5Your nerves and muscles work by moving ions (sodium, potassium) across cell membranes.
Frequently asked questions
- How does an atom become an ion?
- By gaining or losing electrons. An atom with more electrons than protons is a negative ion; with fewer, it's a positive ion.
- What's the difference between a cation and an anion?
- A cation is a positively charged ion (it lost electrons); an anion is negatively charged (it gained electrons). Opposite charges attract.
- Why does salt water conduct electricity?
- Dissolved salt splits into charged ions that move freely, carrying electric current — pure water, with few ions, conducts poorly.