Atoms that have lost or gained electrons are called ions. Ions have the electronic structure of a Noble Gas (Group 0/8).
The elements that most readily form ions are those in Groups 1, 2, 6 and 7.
Group 1 and 2 elements are metals and they lose electrons to form positive (+ve) ions.
Example: Group 1 elements (the alkali metals) form ionic compounds with non-metals where the metal ion has a 1+ charge. E.g. K+ Cl-.
Group 6 and 7 elements are non-metals. They gain electrons to form negative ions.
Example: Group 7 elements (the halogens) form ionic compounds with the alkali metals where the halide ion has a 1- charge. E.g. Na+…