“For the first time in history, a change will be made to the atomic weights of some elements listed on the Table of Standard Atomic Weights of the chemical elements found in the inside covers of chemistry textbooks worldwide. The International Union of Pure and Applied Chemistry’s (IUPAC) Commission on Isotopic Abundances and Atomic Weights is publishing a new table that will express atomic weights of ten elements as intervals, rather than as single standard values.” “The standard atomic weights for hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium previously were expressed as central values with uncertainties that reflected natural atomic-weight variations. The weights of these elements now will be expressed as intervals to more accurately convey this variation in atomic weight. For example, boron is commonly known to have a standard atomic weight of 10.811.
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