Isotope-abundance variations and atomic weights of selected elements

There are 63 chemical elements that have two or more isotopes that are used to determine their standard atomic weights. The isotopic abundances and atomic weights of these elements can vary in normal materials due to physical and chemical fractionation processes (not due to radioactive decay). These variations are well known for 12 elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, magnesium, silicon, sulfur, chlorine, bromine and thallium), and the standard atomic weight of each of these elements is given by IUPAC (International Union of Pure and Applied Chemistry) as an interval with a lower and upper bounds. Graphical plots of selected materials and compounds of each of these elements have been published previously, and herein isotopic abundances, isotope-delta values, and atomic weights for each of the upper and lower bounds of these materials and compounds are provided.