I 1817 begyndte den tyske fysiker [[Johann Wolfgang Döbereiner]] at formulere en af de tidligste eksempler på at klassificere grundstofferne.<ref>{{cite journal|last1=Wurzer|first1=Ferdinand|title=Auszug eines Briefes vom Hofrath Wurzer, Prof. der Chemie zu Marburg|journal=Annalen der Physik|date=1817|volume=56|issue=7|pages=331–334|url=https://babel.hathitrust.org/cgi/pt?id=chi.096071138;view=1up;seq=351|trans-title=Excerpt of a letter from Court Advisor Wurzer, Professor of Chemistry at Marburg|language=de|doi=10.1002/andp.18170560709|bibcode=1817AnP....56..331.}} Here, Döbereiner found that strontium's properties were intermediate to those of calcium and barium.</ref> I 1829 fandt han ud af at han kunne opsætte nogle af grundstofferne i gruppe af tre, hvor grundstofferne hver gruppe havde lignende egenskaber. Han gav disse grupper navnet ''[[Döbereiners triade|triader]]''.<ref>{{cite journal|last1=Döbereiner|first1=J. W.|title=Versuch zu einer Gruppirung der elementaren Stoffe nach ihrer Analogie|journal=Annalen der Physik und Chemie|date=1829|volume=15|issue=2|pages=301–307|url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015065410634;view=1up;seq=315|series=2nd series|trans-title=An attempt to group elementary substances according to their analogies|language=de|bibcode=1829AnP....91..301D|doi=10.1002/andp.18290910217}} For an English translation of this article, see: [http://web.lemoyne.edu/~giunta/dobereiner.html Johann Wolfgang Döbereiner: "An Attempt to Group Elementary Substances according to Their Analogies" (Lemoyne College (Syracuse, New York, USA))]</ref>
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