This model is a complement to the periodic table of elements. Use it to examine the atomic electron shell layout, and to determine the electron configurations that exist in non-excited atoms. The model displays the periodic table with s-elements in red, p-elements in yellow, d-elements in grayish-blue and f-elements in green. Click on any of the element cells to replace the image of the periodic table by the diagram of the chosen atom's electron configuration. Black and gray arrows indicate the full and empty electronic levels, respectively. The window above the electron configuration diagram displays the symbol of the element with a brief description of the electron configuration at the bottom. Add or remove electrons on the diagram by clicking on the arrows that indicate the presence of electrons. After you have changed the electron configuration, push the button "check element existence" in the lower section of the model. If the configuration you have created corresponds to the real configuration of any element, you will see the symbol of this element displayed in the window above the diagram. Otherwise, a message stating that no element in its ground state possesses such electron configuration will appear. You can always return to the periodic table, choose another element, and study its shells filling. To do so, press the "back to the table" button that is located in the lower section of the model.