© Lawrence Berkeley National Laboratory.
The periodic table of elements was devised using an organizing principle based on the observed properties of known elements, which comprise just three ingredients: protons, neutrons, and electrons. Gaps in the original table predicted new elements that were later discovered, confirming that atomic theory was a good representation of reality. The search for new elements continues today, as research teams around the world try to create ever-heavier manmade elements. (Unit: 1)