Chemical Education Today
Plotting the Discovery of the Elements The outstanding October 2009 issue of Journal of Chemical Education, which featured articles on the elements, called to mind an exercise my high school students carried out several years ago to help them become familiar with the elements and the periodic table by recognizing patterns related to the years of each element's discovery. That same exercise also relates to an article in this Journal (1) from 1970. The materials needed at the time were simple: graph paper, a black-and-white copy of the periodic table, colored pencils, and a source of information stating when the elements were discovered. The exercise was carried out early in the school year and was therefore available as a student-created reference when other topics were explored. The students constructed a line plot consisting of a horizontal timeline starting with the 1600s up to the present and using decades as the intervals. A space to the left of 1600 was reserved for elements discovered prior to that time; that space indicated when a particular element was discovered. For elements discovered after 1600, each element's symbol was written above the decade in which it was discovered. If two or more elements were discovered in the same decade, those elements were listed vertically and by atomic number. Once the line plot was completed, students examined the identities of the elements discovered in the same decade and then located them on the periodic table. The students quickly observed that the discovery of elements within a family tended to fall within the same decade, a pattern that surprised and intrigued many of them. They explored questions regarding which elements were among the earliest discovered, why they
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were easily identified, and why hundreds of years passed before more elements were discovered. Determining the decade in which the greatest number of elements were discovered led them to think about other events that influenced those discoveries, including the available technology and the evolving chemical methods and apparatuses. Political considerations ranging from alchemy to spectroscopy to the Manhattan Project even entered the discussions. Along the way, the students realized that the discovery of the elements was not entirely serendipitous but also dependent on the human endeavor. Information readily available on the Internet today makes the initial steps in the exercise somewhat moot. A brief search reveals many sites that list the years of discovery with accompanying pertinent information. Using that information, however, and helping students to recognize why, how, and when the science happened will make them aware of the creativity involved in the scientific process and its dependence on collaboration and communication among colleagues in multidisciplinary fields. Literature Cited 1. Goldwhite, H.; Adams, R. C. Chronology of the Discovery of the Elements. J. Chem. Educ. 1970, 47, 808. Kathleen Thompson* Ocean View, Delaware 19970 *
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Vol. 87 No. 3 March 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc. 10.1021/ed800106b Published on Web 02/09/2010
