IUPAC votes to change standard atomic weights of 19 elements

Sep 26, 2013 by Bob Yirka report

(Phys.org) —The International Union of Pure and Applied Chemistry (IUPAC) has voted to change the standard atomic weight of 19 elements as listed on the Periodic Table of the Elements. The move has come following the annual meeting of a special Union commission held this past August. The changes are being made due to the availability of more precise measurements and have come about as a result of recommendations by the U.S. Geological Survey, commission members and other research organizations.

Weights on the Periodic Table are given as standard atomic weight, which is the average mass of a given element in mass units. One mass unit is equal to 1/12 the mass of a single carbon-12 atom.

Every atom of a single element has, of course, the same number of protons inside its —the number of neutrons can vary however, which identifies the element's various . Making things a little more difficult for high school chemistry students is that the amount of any given element measurable here on Earth varies—and since average mass is used as a measure, the more plentiful an element is, the more it's influenced by how much can be found and measured. Also influencing its weight listed is the precision of the tools scientist use to study the elements. As tools improve and as more samples are studied adding to the amount in an average, researchers move ever closer to more precise weight listings. When that happens, the Periodic Table needs to be adjusted to show what's been found.

Determining precise atomic weights has become more important as new more precise tools are used to investigate the natural world around us. More precise atomic weights help make archeological estimates more precise for example. Scientists have been publishing tables with atomic weights as far back as 1899 when the International Atomic Weights Committee was convened. The IUPAC has been the body responsible for overseeing international standards for since 1919.

In this latest go round, some elements are shown as heavier, some lighter. The full list of changes will be published in a new table tilted "Table of Standard Atomic Weights 2013" in the journal Pure and Applied Chemistry, sometime next year.

Explore further: Modern-day alchemy: A recipe for a new superheavy element

More information: www.iupac.org/news/news-detail/article/standard-atomic-weights-revised-v2.html

Related Stories

Existence of new element confirmed

Aug 27, 2013

Remember the periodic table from chemistry class in school? Researchers from Lund University in Sweden have presented fresh evidence that confirms the existence of a previously unknown chemical element. The ...

A new chemical element in the periodic table

Jun 10, 2009

The element 112, discovered at the Centre for Heavy Ion Research (GSI Helmholtzzentrum für Schwerionenforschung) in Darmstadt, has been officially recognized as a new element by the International Union of Pure and Applied ...

Recommended for you

A greener source of polyester—cork trees

4 hours ago

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

A beautiful, peculiar molecule

7 hours ago

"Carbon is peculiar," said Nobel laureate Sir Harold Kroto. "More peculiar than you think." He was speaking to a standing-room-only audience that filled the Raytheon Amphitheater on Monday afternoon for the ...

Metals go from strength to strength

Apr 15, 2014

To the human hand, metal feels hard, but at the nanoscale it is surprisingly malleable. Push a lump of metal with brute force through a right-angle mould or die, and while it might look much the same to the ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Kedas
not rated yet Sep 27, 2013
We have a more accurate value!
Raise hand if you prefer that value????

More news stories

Breakthrough points to new drugs from nature

Researchers at Griffith University's Eskitis Institute have developed a new technique for discovering natural compounds which could form the basis of novel therapeutic drugs.

A greener source of polyester—cork trees

On the scale of earth-friendly materials, you'd be hard pressed to find two that are farther apart than polyester (not at all) and cork (very). In an unexpected twist, however, scientists are figuring out ...

How kids' brain structures grow as memory develops

Our ability to store memories improves during childhood, associated with structural changes in the hippocampus and its connections with prefrontal and parietal cortices. New research from UC Davis is exploring ...

Gate for bacterial toxins found

Prof. Dr. Dr. Klaus Aktories and Dr. Panagiotis Papatheodorou from the Institute of Experimental and Clinical Pharmacology and Toxicology of the University of Freiburg have discovered the receptor responsible ...