Table of standard atomic weights of the elements 2015

Abstract

Since 1985, the Commission on Isotopic Abundances and Atomic Weights of the International Union of Pure and Applied Chemistry (IUPAC) has disseminated value pairs of standard atomic weight and an associated uncertainty for elements, such that it can claim at a high level of confidence that any element in question in all known normal materials will have an atomic weight that will not differ from the standard atomic weight by more than the uncertainty. The Commission has expressed this decisional uncertainty in parentheses following the value to which it applies, e.g. 78.971(8) for the standard atomic weight of selenium. This presentation is confusing because it suggests to users that 0.008 is the standard uncertainty with a standard deviation of one, which is not intended. To remove this confusion, we provide a 2015 table of standard atomic weights with decisional uncertainty values listed in curly brackets following the last significant digit to which they are attributed.