From the “not etched in stone department”, via Eurekalert we learn that Atomic weights of 10 elements on periodic table about to make an historic change showing that everything we thought we knew, is still subject to revision as we learn more.
Researchers from around the world compile more reliable data that will help science and industry
For the first time in history, a change will be made to the atomic weights of some elements listed on the Periodic table of the chemical elements posted on walls of chemistry classrooms and on the inside covers of chemistry textbooks worldwide.
The new table, outlined in a report released this month, will express atomic weights of 10 elements – hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine and thallium – in a new manner that will reflect more accurately how these elements are found in nature.
“For more than a century and a half, many were taught to use standard atomic weights — a single value — found on the inside cover of chemistry textbooks and on the periodic table of the elements. As technology improved, we have discovered that the numbers on our chart are not as static as we have previously believed,” says Dr. Michael Wieser, an associate professor at the University of Calgary, who serves as secretary of the International Union of Pure and Applied Chemistry‘s (IUPAC) Commission on Isotopic Abundances and Atomic Weights. This organization oversees the evaluation and dissemination of atomic-weight values.
Modern analytical techniques can measure the atomic weight of many elements precisely, and these small variations in an element’s atomic weight are important in research and industry. For example, precise measurements of the abundances of isotopes of carbon can be used to determine purity and source of food, such as vanilla and honey. Isotopic measurements of nitrogen, chlorine and other elements are used for tracing pollutants in streams and groundwater. In sports doping investigations, performance-enhancing testosterone can be identified in the human body because the atomic weight of carbon in natural human testosterone is higher than that in pharmaceutical testosterone.
The atomic weights of these 10 elements now will be expressed as intervals, having upper and lower bounds, reflected to more accurately convey this variation in atomic weight. The changes to be made to the Table of Standard Atomic Weights have been published in Pure and Applied Chemistry and a companion article in Chemistry International.
For example, sulfur is commonly known to have a standard atomic weight of 32.065. However, its actual atomic weight can be anywhere between 32.059 and 32.076, depending on where the element is found. “In other words, knowing the atomic weight can be used to decode the origins and the history of a particular element in nature,” says Wieser who co-authored the report.
Elements with only one stable isotope do not exhibit variations in their atomic weights. For example, the standard atomic weights for fluorine, aluminum, sodium and gold are constant, and their values are known to better than six decimal places.
“Though this change offers significant benefits in the understanding of chemistry, one can imagine the challenge now to educators and students who will have to select a single value out of an interval when doing chemistry calculations,” says Dr. Fabienne Meyers, associate director of IUPAC.
“We hope that chemists and educators will take this challenge as a unique opportunity to encourage the interest of young people in chemistry and generate enthusiasm for the creative future of chemistry.”
The University of Calgary has and continues to contribute substantially in the study of atomic weight variations. Professor H. Roy Krouse created the Stable Isotope Laboratory in the Department of Physics and Astronomy in 1971. Early work by Krouse established the wide natural range in the atomic weight of significant elements including carbon and sulfur. Currently, researchers at the University of Calgary in physics, environmental science, chemistry and geoscience are exploiting variations in atomic weights to elucidate the origins of meteorites, to determine sources of pollutants to air and water, and to study the fate of injected carbon dioxide in geological media.
This fundamental change in the presentation of the atomic weights is based upon work between 1985 and 2010 supported by IUPAC, the University of Calgary and other contributing Commission members and institutions.
The year 2011 has been designated as the International Year of Chemistry. The IYC is an official United Nations International Year, proclaimed at the UN as a result of the initiative of IUPAC and UNESCO. IUPAC will feature the change in the standard atomic weights table as part of associated IYC activities.
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I hereby dedicate 2011 as the year of no longer memorizing non-standard standards.
I’ve never quite understood the logic of declaring a standard weight (shouldn’t that be “mass”?) for elements which can come in a number of isotopes. Why not just list the isotopes separately? They are different, if similar. Averages have their uses statistically, but you are always throwing away information when you take an average.
I wonder if this makes any difference to the recorded proportion of fossil v contemporary CO2 in the atmosphere which is measured using the isotopes that have just been “re-expressed”?
My loving wife, a chemical engineer and AP chemistry teacher, will NOT be happy. 8<)
"I", being an astute and debonair nuclear engineer, consider the electrons around the nucleus as being "not worth the interest" and, since they weigh less than 1/1800 the mass of the "real world" particles, "obviously" can be neglected as rounding errors in the grander scheme of data collection. 8<)
GISS and Micheal Mann would approve.
‘to study the fate of injected carbon dioxide in geological media.’
Goodness, I wonder why? Forgive my layman’s cynicism but is this what all this research has really been about?
“Though this change offers significant benefits in the understanding of chemistry, one can imagine the challenge now to educators and students who will have to select a single value out of an interval when doing chemistry calculations,” says Dr. Fabienne Meyers, associate director of IUPAC.
For a statistician, all measurements are imprecise, and therefore should be accompanied by a probability statement. Sounds like Statistics will be required. I wonder how all those semi-literate hormone driven kids will cope with that?
My wife’s atomic weight fluctuates also. Her density remains constant.
The atom still holds a world of secrets. Those models with balls and sticks will be laughed at someday.
Here’s to not being afraid to change the model when knowledge is gained.
Interestingly 2 of the elements are C and O.
With 2011 as the International Year of Chemistry, perhaps the UN IPCC can find some scientists to reexamine its assumptions about the properties of CO2 and find a different consensus on its effects as a greenhouse gas.
Nice to see this leading research coming out of the University of Calgary.
And won’t it be great when Anthony’s blog can spend more time on “other puzzling things” because the climate change phenomenon will have run it’s course? 2011 may indeed be the begining of the end of AGW.
So much for “settled” science. 😉
I seem to recall a change in atomic weights far less than 100 years ago, when the IUPAC decided to make carbon-12 a standard. Prior to that, the atomic weights were referenced to oxygen. After that, C12=12.000 was set, all the atomic weights shifted a bit, and the atomic weight of native carbon itself became 12.011.
I’ve now checked, and Wiki has an article that mentions this.
This doesn’t look like a big shakeup in the science of chemistry. From the sulfur example, it looks like there is just some uncertainty in the last digit of the old standard value(from -.006 to +.011 in a presumably extreme example). Any good chemistry teacher should have explained that the atomic weights were for the common isotope proportion and could vary. My chemistry teacher explained it more than ten years ago.
The periodic table given above is fairly old…….
The elements 110, 111 and 112 have been named as follows:
110 : Darmstadtium
111 : Roentgenium
112 : Copernicium
Forgot the atomic symbols:
110 : Darmstadtium (Ds)
111 : Roentgenium (Rg)
112 : Copernicium (Cn)
Great! Now I have all these books that are obsolete.
Actually, my most recent buy was a nice surprise. From the title I thought the text was going to be a bit hokey, but I found it very interesting. I recommend it for anyone with an interest in chemistry or the history of science. See:
http://www.amazon.com/Disappearing-Spoon-Madness-Periodic-Elements/dp/0316051640
Oh please. Forget electrons. Whatever happened to just adding up the protons and neutrons.
“one can imagine the challenge now to educators and students who will have to select a single value out of an interval when doing chemistry calculations”
This is a problem only for those who like to calculate to a precision beyond that justified by their experimental knowledge. See it as an object lesson in significant figures.
To Ian B
You rarely work with pure isotopes. Thus you need the effective (average) value for the reagent at hand in order to calculate the proper concentrations for solutions in your chemistry experiment. That is, you need to know the number of atoms or molecules you are adding.
Ian B
The way elements are used by chemists and others involve using them as they are found in nature. They are shoveled or scooped around to make stuff (solutions, compounds etc. such as sulfuric acid from sulfur). It is necessary to know the atomic weights as they are in the sample being used. The weights on the periodic table are a weighted average of the mixtures of isotopes as they are most commonly found in nature. Different ore deposits may have a different isotopic mixture so the weights may be slightly different from one ore body to another, but the numbers we are used to seeing are what has been found to best represent isotopic abundances from samples that were known and used historically. Some branches of science such as nuclear studies need to work with specific isotopes but most do not.
Add to that, scientists now think the neutrino has non-zero mass and some previously declared physical constants may not be constant across the universe, and we have the makings of some big changes in Physics.
This isn’t really a change in what we know. I think it’s more a change in how that information is presented on the table.
It is an interesting difficulty. There isn’t enough room in those little boxes to lay out the natural abundances of each isotope, and also explain that the proportions in any given system might differ from those listed.
The onus is on the user to know when he has to worry about isotopic compositions. Perhaps this approach will make that more obvious.
Wow! Just Wow! I will write the new ranges on my chem element chart. Wonderful post, and comments at least as good and entertaining. Makes jury deliberations palatable — or at least bearable — to come home to monumental news.
The more man learns, he finds, the less he knows. For instance … What we know about global warming, you might be able to write a decent paper. But what we don’t know about global warming, you could fill a large library.
Such is the ways of nature.
I wonder what people who lived in the 9th century thought of global warming? Or did they just move to Greenland.
Curiousgeorge says:
“For a statistician, all measurements are imprecise, and therefore should be accompanied by a probability statement. Sounds like Statistics will be required. I wonder how all those semi-literate hormone driven kids will cope with that?”
My daughter just got home from her first semester in college. Got an A in Physics, an A in Chem Lab, probably has an A in Chemistry and an A in Calculus. She graduated 5th out of 500+ from high school. I on the other hand an completely average and would not want to have to take Chemistry again.
@ur momisugly Myron Mesecke says:
December 15, 2010 at 6:44 pm
Congratulations to your daughter. I did not mean to imply that all hormone driven kids are semi-literate. Some are not, of course. 🙂