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Revised Periodic Table

January 11, 2011

The Periodic Table of the Elements gets its first significant revision in over half a century.


Revamping a classroom icon…I’m Bob Hirshon and this is Science Update.

The Periodic Table of the Elements, seen on the walls of chemistry classrooms everywhere, is in for a historic change. For the first time, the atomic weights of ten elements, including hydrogen, carbon, and oxygen, will be stated as a range instead of a single number. Ty Coplen of the U.S. Geological Survey says that’s because some elements exist in different forms, called isotopes, some of which are more abundant than others.

TY COPLEN (Reston Stable Isotope Lab, U.S. Geological Survey):
What we want to do is make that clear to students and teachers, that in fact these variations exist, and that atomic weights are not constants of nature.

The “we” he’s referring to is the International Union of Pure and Applied Chemistry. Advances in research and technology have made it possible to pinpoint the upper and lower limits of atomic weight ranges, rather than just give an average. I’m Bob Hirshon, for AAAS, the science society.