Ions
Ions are atoms that have gained or lost electrons.
About this topic
An ion is an atom or group of atoms with a net electric charge, formed by gaining or losing electrons. Losing electrons gives a positive cation, as metals usually do; gaining electrons gives a negative anion, as non-metals usually do. Ionic charge relates to group number: group 1 forms +1, group 2 forms +2, group 17 forms -1 and group 16 forms -2.
Atoms form ions to reach a stable full outer shell. Sodium has one valence electron and loses it to become Na+ with the electron arrangement of neon, while chlorine gains one to become Cl- with that of argon. Only electrons move; the nucleus, and therefore the identity of the element, never changes. Ions are written with the charge as a superscript, and the ion has very different properties from the atom: sodium metal reacts violently with water, but sodium ions are everywhere in your body.
Ions do important jobs. Sodium and potassium ions carry nerve signals, calcium ions build bones, and dissolved ions let solutions conduct electricity in batteries and sports drinks.
Students often think that cations are larger than their atoms; they are smaller because losing electrons shrinks the cloud, while anions are bigger. Also, the number of protons does not change when an ion forms.
Key ideas
- Cations are positive
- Anions are negative
- Metals form cations, non-metals form anions
Quick check
Use cases: where Ions helps
- Homework: review the key idea behind Ions before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Ions without notes.
- Visual learning: play with the interactive lab to see how Ions changes when you adjust its inputs.
- Teaching a friend: explain Ions in your own words, then compare your version with the key ideas.
Chemistry explains medicine, food, cleaning products, fuels and building materials.
Frequently asked questions
What is Ions?
Ions are atoms that have gained or lost electrons.
What will I learn in Ions?
Cations are positive. Anions are negative. Metals form cations, non-metals form anions.
Is Ions part of Chemistry?
Yes. It is one of 150 Chemistry topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Ions lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Ions?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.