En el lugar de Mendeleev: experiencia didáctica de ordenación de elementos químicos

Abstract

This work presents a didactic experience carried out with first-year university students, before the systematic teaching of the unit: "Periodic relationships between the elements". The objective was to evaluate the implementation of an ordering activity for chemical elements in a table, based on information on some properties of these elements. In such a way as to emulate, in a simplified context and for educational purposes, the precursors of the periodic table. The activity consists of ordering 32 elements, the representative elements of periods 2 to 5 (from Li to Xe) in a table of 4 rows and 8 columns, according to similar regularities or trends. The activity provides data on properties that are addressed in general chemistry courses: atomic mass, atomic radius, boiling point, first ionization energy, electronic affinity, and oxidation number. These properties were selected for being the ones that best allow us to observe patterns. To avoid the influence of prior knowledge, elements with fictitious symbols and property values proportional to the real ones were used. These data were presented in a table in increasing order of atomic mass and in 5 graphs of these properties versus atomic mass. It was observed that 9 of the 13 students who participated in this preliminary and virtual activity, arrived from the available data to a table, to a periodic ordering. Although the majority did so taking into account, fundamentally, the repetition of the oxidation number. Results are discussed and conclusions and projections are issued.