Why has the bohr-sommerfeld model of the atom been ignoredby general chemistry textbooks?

Bohr's model of the atom is considered to be important by general chemistry textbooks. A major shortcoming of this model was that it could not explain the spectra of atoms containing more than one electron. In order to increase the explanatory power of the model, Sommerfeld hypothesized the existence of elliptical orbits. This study has the following objectives: 1) Formulation of criteria based on a history and philosophy of science framework; and 2) Evaluation of university-level general chemistry textbooks based on the criteria, published in Italy and U.S.A. Presentation of a textbook was considered to be "satisfactory" if it included a description of the Bohr-Sommerfeld model along with diagrams of the elliptical orbits. Of the 28 textbooks published in Italy that were analyzed, only five were classified as "satisfactory". Of the 46 textbooks published in U.S.A., only three were classified as "satisfactory". This study has the following educational implications: a) Sommerfeld's innovation (auxiliary hypothesis) by introducing elliptical orbits, helped to restore the viability of Bohr's model; b) Bohr-Sommerfeld's model went no further than the alkali metals, which led scientists to look for other models; c) This clearly shows that scientific models are tentative in nature; d) Textbook authors and chemistry teachers do not consider the tentative nature of scientific knowledge to be important; e) Inclusion of the Bohr-Sommerfeld model in textbooks can help our students to understand how science progresses.

Did Columbus hypothesize or predict that if he sailed due west, he would arrive at the Indies?

A review of the literature in science education shows that most students have difficulties in hypothetico-deductive reasoning. The author's objective in this study was to investigate the abilities of high school teachers and university teachers to understand the difference between the terms hypothesis and prediction in the everyday context of Columbus's discovery of America. The author asked 83 high school and university teachers enrolled in a methodology course to elaborate and to explain a prediction and a hypothesis based on Columbus's discovery. Results, based on written responses, showed that most teachers (approximately 60%) did not understand the difference between a hypothesis and a prediction. The author also observed that many teachers did provide a satisfactory description of what they considered to be a hypothesis and a prediction. However, the difficulty for the teachers consisted in operationalizing (elaborating and understanding) the difference between a hypothesis and a prediction. Some teachers explicitly elaborated and classified a prediction as a hypothesis and, at times, the teachers elaborated the two terms in the same manner, without being aware of the contradiction. The study has educational implications by showing that, just like students, teachers have difficulties with the elaboration and understanding of the concepts of hypothesis and prediction. Given the importance of such concepts for all research programs, it is essential that appropriate teaching strategies be implemented.

Achievement in chemistry problem-solving as a function of the mobility-fixity dimension.

The present studies explored the relation between students' achievement in chemistry problem-solving and the Mobility-Fixity dimension. Fixity characterizes consistency of function of field-independent subjects in a field-independent fashion, while Mobility provides for variation according to circumstances. The effect of this cognitive variable was examined as a function of the type and the complexity of the problem. Two kinds of problems were used, chemical equilibrium problems with varying mental demand and logical structure, and organic synthesis problems with varying mental demand. The subjects had to carry out different mental tasks, such as manipulation of logical schemata, applying algorithmic procedures, solving nonalgorithmic problems. In all cases, Mobile subjects demonstrated higher achievement than Fixed subjects. The results of this study support the hypothesis that the Mobility-Fixity dimension can serve as a predictor variable of students' performance on chemistry problem-solving.