Elements Get An Atomic Weight Makeover

For the first time in history, the standard weights of 10 elements will get expressed in a way that will more accurately reflect how the elements are found in nature. Melissa Block and Michele Norris explore the implications.

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MICHELE NORRIS, host:

Marie Curie was once a member of the Commission on Isotopic Abundance and Atomic Weights. That group tells the world what the atomic weights are for every chemical element used in trade and commerce.

What they publish winds up on those chemistry wall charts you may remember from high school, called the Periodic Table of Elements, and includes those atomic weights. The commission is changing the value for those atomic weights. Instead of just one number, from now on they will show a range of values. Research chemist Tyler Coplen.

Dr. TYLER COPLEN (Research Chemist, U.S. Geological Survey): The concept that we're trying to get across to students by doing this is to indicate to them that these atomic weights are not constants of nature, but they vary, and they vary because there are different portions, different fractions of stable isotopes in materials.

MELISSA BLOCK, host:

Now, there are some elements, such as gold and aluminum, that do have stable weights. Others are radioactive and have no standard atomic weight, such as radium. Coplen says in the future, more elements may get an atomic weight makeover.

Dr. COPLEN: My daughter Wendy says to me: Dad, you've just made chemistry harder for everybody.

NORRIS: But more accurate. Coplen says the variation in isotopes is a useful tool for, among other things, checking on the purity of food products. Changing the periodic table is just a way to illustrate that for students.

So all those pull-down charts and textbooks that carry the Periodic Table of the Elements will now have to be updated. Will Coplen get any kind of kickback from those manufacturers?

Dr. COPLEN: I missed that. I should have thought ahead. But no, I'm not.

BLOCK: That's research chemist Tyler Coplen, explaining the changes to how the atomic weights of 10 elements will be shown on the periodic table.

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