Each cell of the Periodic Table of Elements and Isotopes provides the chemical name, symbol, atomic number, and standard atomic weight of an element. A pie chart displays the proportion of each isotope of the element.
The background of each element cell is color-coded and displays the stable isotopes and the relatively long-lived radioactive isotopes having characteristic terrestrial isotopic compositions that determine the standard atomic weight of each element. This background color scheme of cells classifies the 118 elements into four groups: (1) white indicates the element has no standard atomic weight, (2) blue indicates the element has only one isotope that is used to determine its standard atomic weight, which is given as a single value with an uncertainty, (3) yellow indicates the element has two or more isotopes that are used to determine its standard atomic weight, which is given as a single value with an uncertainty, and (4) pink indicates the element has a well-documented variation in its atomic weight, and the standard atomic weight is expressed as an interval.
