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.
Leanne Yohemas | EurekAlert!
During HIV infection, antibody can block B cells from fighting pathogens
14.08.2018 | NIH/National Institute of Allergy and Infectious Diseases
First study on physical properties of giant cancer cells may inform new treatments
14.08.2018 | Brown University
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur
What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...
The quality of materials often depends on the manufacturing process. In casting and welding, for example, the rate at which melts solidify and the resulting microstructure of the alloy is important. With metallic foams as well, it depends on exactly how the foaming process takes place. To understand these processes fully requires fast sensing capability. The fastest 3D tomographic images to date have now been achieved at the BESSY II X-ray source operated by the Helmholtz-Zentrum Berlin.
Dr. Francisco Garcia-Moreno and his team have designed a turntable that rotates ultra-stably about its axis at a constant rotational speed. This really depends...
08.08.2018 | Event News
27.07.2018 | Event News
25.07.2018 | Event News
14.08.2018 | Information Technology
14.08.2018 | Life Sciences
14.08.2018 | Life Sciences