Specification Point 1.37:
Understand how ions are formed by electron loss or gain

How Ions are Formed

An ion is an electrically charged atom or a group of atoms that are formed by the loss or gain of electrons.

  • This loss or gain of electrons leave a full outer shell of electrons.
  • The electronic structure of an ion will be the same as that of a noble gas – such as Helium, Neon and Argon.

Ionisation of metals and non-metals:

  • Metals: They will lose electrons to another atom and become positively charged ions
  • Non-metals: They will gain electrons from another atom to become negatively charged ions


Positive sodium and aluminium ions, CIE IGCSE Chemistry

Positively charged sodium and aluminium ions


Negative oxide and chloride ions, CIE IGCSE Chemistry

Negatively charged oxide and chloride ions

Share with friends

Aiming for a Level 9?

See if you’ve got what it takes. Test yourself with our topic questions.

Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.