Communication pubs.acs.org/jchemeduc
ConfChem Conference on A Virtual Colloquium to Sustain and Celebrate IYC 2011 Initiatives in Global Chemical Education: The IUPAC Periodic Table of Isotopes for the Educational Community Norman E. Holden*,† and Tyler B. Coplen‡ †
Brookhaven National Laboratory, Upton, New York 11973, United States U.S. Geological Survey, Reston, Virginia 20192, United States
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S Supporting Information *
ABSTRACT: The IUPAC Periodic Table of the Isotopes (www.ciaaw.org) was prepared as an educational outreach effort to expose teachers, students, and the general public to the existence of both stable and radioactive isotopes of the chemical elements. This Table provides information on the isotopes of each element, including the mass number and fraction of each isotope in a stable or a long-lived radioactive chemical element. These data allow scientists to determine the atomic weight of each element, which connects the microscopic and the macroscopic worlds. For many elements, there is a variation in the fraction of an element’s isotopes in naturally occurring substances. The atomic weight is variable beyond its measurement uncertainty and the upper and lower bounds of the standard atomic weight are presented as an interval, rather than as a value with uncertainty, for 10 elements. The Table provides examples of the importance of both the stable and radioactive isotopes in our everyday world because of the variability of the stable isotope ratios or the radioactive decay of the unstable isotopes. There are 440 examples of applications to our everyday life. Applications, such as medical, industrial, geo-chronological, earth and planetary science, biological and forensic science, and anthropological are shown. Readers of the conference paper responded with questions, and the answers to the questions are included. This communication summarizes one of the invited papers to the ConfChem online conference A Virtual Colloquium to Sustain and Celebrate IYC 2011 Initiates in Global Chemistry Education held from May 18 to June 28, 2012, and jointly hosted by the ACS DivCHED Committee on Computers in Chemical Education and the IUPAC Committee on Chemistry Education. KEYWORDS: Continuing Education, General Public, Inorganic Chemistry, Public Understanding/Outreach, Isotopes, Nuclear Radiochemistry, Periodicity/Periodic Table
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scientists to determine the relationship between the microscopic and the macroscopic worlds. From the beginning of the 19th century until the middle of the 20th century, atomic weight values were considered to be “constants of nature”. Measurements of the isotope ratios in elements have indicated that there is a variation in nature for many of these elements. As a result, the measurement of the atomic weight value may vary in some terrestrial samples with values that exceed the measurement uncertainty. To indicate the variability in the atomic weight of such elements, intervals have been assigned to recommended atomic weight values for 10 chemical elements in the past few years (H, Li, B, C, N, O, S, Si, Cl, and Tl). For example, Figure 2 presents the box for sulfur in the periodic table. As time goes on and more samples are measured with better precision, there may be additional elements, whose atomic weight values will need to be assigned with these intervals. We present information on both the stable and the unstable or radioactive isotopes of each element. Not all of the isotopes
his IYC-2011 project exposed teachers, students, and the general public to the concept of isotopes of the chemical elements with presentation of the IUPAC Periodic Table of the Isotopes (IPTI), a legend of which is shown as Figure 1. We point out that knowledge of isotopes, their mass, and the fraction of each isotope in a stable or long-lived chemical element allows scientists to determine the atomic weight of the element. In turn, the atomic weight of the element enables
Figure 1. One of the legends of the IUPAC Periodic Table of the Isotopes is given, exemplifying the element cadmium. See www.ciaaw. org. © 2013 American Chemical Society and Division of Chemical Education, Inc.
Published: October 8, 2013 1550
dx.doi.org/10.1021/ed3008236 | J. Chem. Educ. 2013, 90, 1550−1551
Journal of Chemical Education
Communication
(University of Calgary, Canada), and S. Yoneda (National Museum of Nature and Science, Japan). This paper was discussed from June 1 to June 7 during the spring 2012ConfChem online conference, A Virtual Colloquium to Sustain and Celebrate IYV 2011 Initiates in Global Chemical Education. This conference was jointly hosted by the ACS DivCHED Committee on Chemistry Education, and can be accessed at http://www.ccce.divched.org/spring2012confchem .
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ASSOCIATED CONTENT
S Supporting Information *
Figure 2. Graphic for sulfur shows the standard atomic weight, which is now an interval.
Full paper from the ConfChem conference. This material is available via the Internet at http://pubs.acs.org.
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of a stable element are, in fact, stable isotopes. Chemical elements may contain no stable isotopes, one stable isotope, or more than one stable isotope. We stress the importance of both stable and radioactive isotopes in the everyday world of the individual. For example, a radioactive isotope of the element americium (of mass 241) should be familiar to almost everyone because it is the source that enables smoke detectors in our homes to alarm and warn us if there is a fire in the house. Although we could not supply all of the examples of the usefulness of isotopes of the elements in real life, this project does provide importance of a significant number (440) of them. Readers of this paper have responded with a series of questions. Issues, about the fact that stable isotopes are fractionated by physical and chemical processes, have led to a discussion about the use of these fractionated isotopes. The result of this fractionation is that substantial use is made in investigations in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic applications, geochemistry, geology, oceanography, and paleoclimatology. Questions allowed us to provide information on the binding energy and why the mass of a given isotope is not equal to the sum of the masses of the neutrons, protons, and electrons that make up the atom. Questions also allowed us to correct the designation of calcium-40 as a radioactive isotope. A half-life measurement was actually an upper limit. Proof of the radioactive decay of Ca-40 was not verified and it is now designated as a stable isotope. The full project lists more than 3000 radioactive isotopes as well as the 252 stable isotopes of the elements. This project lists 440 applications of both stable and radioactive isotopes in our everyday life. The project informs teachers, students, and the public about the necessary and useful role played by the isotopes of the chemical elements. These 440 applications are divided into seven different general categories. We list 121 medical applications in 61 elements, 76 industrial applications in 38 elements, 70 earth and planetary science applications in 41 elements, 60 geo-chronological applications in 38 elements, 53 radioactive source production applications in 33 elements, 36 biological applications in 20 elements, and 24 forensic science and anthropological applications in 10 elements. The project would not have been possible without the expert contributions of J. K. Böhlke (U.S. Geological Survey), P. G. Mahaffy (King’s University College, Edmonton, Canada), G. O’Connor (U.S. Department of Energy), L. V. Tarbox (U.S. Geological Survey), D. H. Tepper (U.S. Geological Survey), T. Walczyk (National University of Singapore), M. E. Wieser
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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dx.doi.org/10.1021/ed3008236 | J. Chem. Educ. 2013, 90, 1550−1551
