Elements in the same family are located in the same column of the periodic table. One example of a family is the halogens.
The halogens have seven valence electrons. Valence electrons are shown as dots around element symbols on Lewis structures (dot diagrams). Please note that He has only two valence electrons, the rest of the Noble gases have eight valence electrons.
The oxidation state of simple ions (from one atom) is the same as the charge of the ion. Halogens will gain one electron to fill their valence shell to form ions. This means they will have a charge of -1.
Here is a review of how ions form.
Hope this helps!