Strangely enough when an atom loses electrons it becomes positively charged and when in gains electrons in becomes negatively charged.
When one atom loses electrons to another atom, for example Sodium Chloride. Sodium loses one electron to chlorine, so sodium becomes Na+ and chlorine becomes Cl-, these are Ions.
And as opposites attract, they join together, this is called an Ionic Bond.
An example of a more complicated Ionic bond is Calcium Chloride:
Test Yourself At http://www.quia.com/jq/19617.html =]
