The periodic table becomes a weight watcher

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.

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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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58 thoughts on “The periodic table becomes a weight watcher

  1. 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.

  2. 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”?

  3. 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.

  4. ‘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?

  5. “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?

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. “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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. @ 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. :)

  20. I LOVE electrons! It’s akin to erector sets! Without the connectors, how do you build H2O? There is no better or more fun experiment than building a molecule. Who wants to paint with the primary colors???? I like to mix things up. And without electrons, my experimental fun is ended!

    A case in point, I discovered that zirconium burns quite readily. That’s cool. But the jewel we all know as zircon (ZrSiO4) is as beautiful, if not more so, than diamonds. All because of electrons attracting each other between different elements.

    Electrons rule, nucleus stuff drools!

  21. Hmm, I wonder if the chemists were feeling a bit left out? you know with all this meteorological ‘science’, climate science, earth science, physics, geophysics, etc, etc – all being dragged headlong into the AGW arena – the chemistry side has been rather ‘lacking’ in its input?
    Perhaps, they thought if they put a ‘range’ on some common elements, it would enable them to get more involved re-doing some calculations and giving error bars, etc! LOL
    (ps -only joking, before any chemists get stressed out!)

  22. “Forget electrons. Whatever happened to just adding up the protons and neutrons.”

    OK, let’s try that.

    H-1= One proton, (and one electron) so the atomic mass is 1, right? No, it’s 1.007825.
    H-2= One proton, one neutron (and one electron)… mass=2? Nope: 2.014102.

    You may have noticed that H-2’s mass is not QUITE double what H-1’s mass is. The difference is the Nuclear Binding Energy, and it’s very important. As you add protons and neutrons to make larger nuclei, this binding energy is larger than the constituent parts, which is what powers the Sun. The binding energy per nucleon hits a pretty big local maximum at He-4, and doesn’t rise above it until the next local maximum, C-12. From there it falls off slightly, but generally increases until the absolute max. of Fe-56, which has a mass of only 55.934937 atomic mass units. Below that max, fusion generally releases energy, and fission absorbs it. Above that level, fusion absorbs energy and fission releases it, as the average binding energy per nucleon slowly falls off.

    The AMU itself was defined by arbitrarily assigning C-12 the exact mass 12.

  23. 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.

    Get Albert Pujols and Manny Pacquiao in line for the test now.

  24. Richard M says: 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.

    Odd you should mention that… I’ve just collected a set of Feynman talks here:

    http://chiefio.wordpress.com/2010/12/15/on-the-sillyness-of-consensus/

    and in the one of them he discusses the probability that the laws of physics ‘evolved’ over time and may not have always been constant… (Which implies they might still be changing today.)

    Part 3 of 4 of taking the world from “another pont of view”:

    (It helps a little to have the whole set in order at the top link, but if you have some physics background you can drop in directly here.)

  25. Does this mean that Tom Lehrer is going to have to redo his great song!

    Although as a good scientist he does leave room for change in what is known in the last line.

  26. Revised raw data again. Outrageous!
    I’ll have raw vs GISS homogenized blink charts for hydrogen, lithium, boron, carbon, and nitrogen up in a jiffy.
    I don’t have Version 1 for oxygen, silicon, sulfur, chlorine, and thallium.

  27. How dare they let the scientific method get in the way of years of concensus. That’s no way to practice science!

  28. @anthony

    “everything we thought we knew, is still subject to revision as we learn more”

    Yabbut in this case nothing new was learned. It’s just a change in notation akin to changing gasoline pumps so they indicate pounds of fuel pumped instead of gallons. Except that would be a good change where this periodic table change is just the grand exalted mystic poobah of standard weights and measures doing nothing more significant than a dog peeing on a tree because a) he wants to make a mark for posterity and b) because he can.

  29. 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
    ————-
    I don’t believe it’s the first time in history.

  30. Phil’s Dad says:
    December 15, 2010 at 4:09 pm
    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”?
    ———–
    The isotopic masses have not changed.
    The CO2 in the atmosphere is diagnosed using ratios of numbers of molecules (essentially). So it’s not relevant.

  31. “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.”

    I can’t imagine how young people will control themselves.

  32. “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.”

    Is this the “nature of the solar system” or the “nature of the local group” or the nature of the universe”? Besides, high school kids are having enough trouble these days on the web getting the right answer, so what’s the good gained by messing up the google search for the right, “new” periodic table? Modern Education sucks! (SarcOff)

  33. James B;
    yaass — “This is all the elements, Of which the news has come to Hahvard; There may be many others, But they haven’t been discahvered!” His most dramatic elemental reference was, IMO, “When they see us coming, The pigeons all try’nhide, But they still go for peanuts When covered with cyanhiiide …!” Such a sweetheart!
    ——
    That collection of changing elements put me strongly in mind of my favorite ongoing experimental project: p + B11 –> C12 –> 3 He4 . Plus lotsa energy. At LPPX.com .

  34. Hm, “These are”? “This is”? Memory fails … grammar is ambiguous …

    OK, went back to my mp3 of the song: “These are the only ones of which the news has come to Hahvard; And there may be many others but they haven’t been discahvered.”

  35. Then Carbon will change to GORENIUM?, Lead will be called Hansenium, Sulphur Mannenium, and so on :-)
    I suspect that from that change on, it will not reflect anymore its correspondence with the various frequencies of the musical octave, as the original Mendeleev table shown.
    A similar attempt was unsuccessfully tried when, after the French Revolution, it was established a square angle of 100 degrees (!!) or a circle of 400 degrees (!!), etc.
    Its purpose: To disrupt any possible relation with a Logos. In other words, to secularize the world.

  36. E.M.Smith says:
    December 15, 2010 at 8:48 pm
    …the laws of physics ‘evolved’ over time..
    Global Governance is about confusion…
    This universe, which is the same for all, has not been made by any god or man, but it always has been, is, and will be an ever-living fire, kindling itself by regular measures and going out by regular measures.
    Heraclitus of Ephesus

  37. Being a scientist involved in FTMS mass spectrometry, I do take the electrons into account. And every accurate mass (6 decimals) of any isotope of any element present in an unidentified metabolite. And the isotopic ratio of isotopes of one element, which does indeed allow to discriminate between the origin of the molecule in question.

    If not I will unneccesarily increase the number of possible molecular formulas.

  38. dbleader61:

    You suggest;
    “2011 may indeed be the begining of the end of AGW.”

    No. The begining of the end of AGW was in 2009. It happened in Copenhagen.

    Richard

  39. I’ve lost interest in what these new kids on the block have to say since they demoted Pluto.

    In my world and Solar sytem Pluto is still a planet!

    And AGW is manure!

  40. Good to see that Sodium is not on the IUPAC update list.
    At a social gathering, a few women were upset that the men in their lives didn’t seem to remember things they deemed important. As the discussion forged on, I asked the woman sitting next to me … “What is the molecular weight of Sodium?” When she asked who could possibly need to know that, I told her it was a number that I used regularly, and had committed to memory. At least a few people chucked, which was my intent in mentioning it. Please don’t think I am trying to start a women vs men argument. My point of view in that discussion was that we are all exposed to so much information that sometimes the ‘new’ can crowd out the ‘old’ in our day to day working memory. True story, as best I remember it. :)

  41. I, for one, cannot express how happy I am that I’ve never had a teacher who made me memorize any part of the periodic table. After eight years of chemistry research, I can definatively say that I have never been more than a few clicks or 10 feet away from a table whenever I needed one. Ironically however, if they ever change those elememts I use the most, it would really throw me for a loop, as just by sheer use, I’ve memorized some values.

  42. Some one raised the Men V Women debate (Women are actually from Pluto. And we know what happened to Pluto!) Anyway. The debate is sorted via the Public Information Announcement listed below from Youtube.

    http://www.youtube.com/view_play_list?p=FFF74E14405C2957&playnext=1&v=2jV6Kc5wTwA

    As for the periodic table: Remember; Decay rates are affected by cycles on the the Sun by either Teleconnection, A unknown flavour of Neutrino, or something even more weired.

  43. I like a bit of comedic relief on the weekend.

    Cheers to everyone @ WUWT on a spectacularly succesful 2010!!!!!!!

  44. Ladies: Even gentleman Chemists, without a current map of the periodic table, has contractual conjugal rights you know. Don’t you, chaps??

    I rest my case.

  45. Enneagram says:
    December 16, 2010 at 6:33 am

    I suspect that from that change on, it will not reflect anymore its correspondence with the various frequencies of the musical octave, as the original Mendeleev table shown.
    A similar attempt was unsuccessfully tried when, after the French Revolution, it was established a square angle of 100 degrees (!!) or a circle of 400 degrees (!!), etc.
    Its purpose: To disrupt any possible relation with a Logos. In other words, to secularize the world.

    No, no, no.

    Any world where a circle can be built by the square value of Pi with 100 degrees quadrant is known as a Legolos, not a Logos.

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