What is the difference between an ion and an atom?
Atoms are neutral particles, ions have a charge.
Atoms are neutral because they have an equal number of protons (+) and electrons (-).
Ions are charged particles which are formed when atoms either gain or lose electrons. When atoms gain or lose electrons they become more stable.
Here is a review of what happens when ions form.
And here is a review of the basic structure of atoms...
Hope this helps!