The valence of an atom is its oxidation state. For example, a sodium atom usually has a +1 charge, while oxygen most often has a -2 charge, and chlorine usually has a -1 charge. Keep in mind, technically an atom can carry any charge. This table lists the most common.
Color Periodic Table of the Elements with Charges
This color periodic table contains the most common valence charges of the elements.
This table also contains the element number, element symbol, element name, and atomic weights of each element.
The periodic table in PDF format can be downloaded.
More Periodic Tables
A black and white version of this table for those without color printers is also available.
More downloadable periodic tables for wallpapers or printing are available online. These are tables which include all 118 elements and recent atomic data.