The amazing periodic table

The Amazing Periodic Table The study of the periodic tahle is a vital part of any chemistry curriculum. I t is surely the single most important tool available to organize the vast amount of chemical information known today. The typical introductory textbook describes the oeriodic tahle in ereat detail. but little or no attemot is made t o ooint out how amazine i t is that such a simole nattern

my beginning students. I ask a dozen boys to line up in front of the class in order of increasing height. The rest of the class is then told to look for patterns. For example, usually several boys are wearing glasses, and attention is focused on the students just to the rixht of each boy with glass&. Careful scrutiny does not reveai any consistent pattern of similarities among this group. After a few more attempts a t pattern finding the boys are sent back to their seats with thanks. I then turn t o the hlarkboard and list the first 20 elements in order of increasine atomic number. The similarities of He,tie, and Ar arc noted. Then the clcmrnta jusl tu the right ufrach of tlww clemcntinrr t'ound t u rrsemhleme another. but with very differentpnqwrtie5 than the n d h g a s m . tirrr thsrlemenrs to thelcft of carhofthe inert aair.are cxumiwd. andagain t h ~ ya r e f w n d t u haw similarche~nicalpmpertws.Ar rhisptinr I usuall) rewrite the list o i r l r r w t ~ t in s the rlwal periodic table format and continue t o check for the presence of additional chemical families. At the end of this session students have a good idea of the expermental basis for the periodic table, and an appreciation of how astounding it is that such unexpected order exists in the world. ~~~~~

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James Flnholt Carlton College Northfield. MN 55057

190

Journal

of

Chemical Education