How They are fomed
How they are formed
When an atom gains or losses an electron to have full valence, an ion is formed.
Why ions form
They form so that the atom can have full valence in the highest energy level.
What kind of ions form.
If they lose an electron its called a "cation". If it gains electrons then its called an "anion"
How to determine the charge
If its an anion it has an overall negative charge. If its a cation it has an overall positive charge.