Atomic weights were previously thought to be constant values with a level of uncertainty; however, the atomic weights for hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, and thallium are now expressed as intervals to more closely reflect the variations these chemical elements have shown.
While this is an exciting discovery, one can only image the magnitude of replacing the now outdated periodic tables that have decorated the inside covers of chemistry books and classroom walls throughout the world. To address this issue, the International Union of Pure and Applied Chemistry (IUPAC), with the assistance of the Committee on Chemistry Education (CCE), created the project, Development of an isotopic periodic table for the educational community. The goal of the project was to create an interactive periodic table to display the new isotopic information. All levels of education could then use the new table and students will have immediate access to the latest information.