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- Nimmermark, Anders, 1971
(författare)
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Facets of chemical bonding that enhance or encumber conceptual understanding
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chemical bonding is a vast subject, rich in abstract concepts and advanced and less-advanced explanatory models that the learner has to master. In this context, the teaching of chemical bonding at the secondary school level is extremely important, as it has the potential to increase or hinder students’ further understanding of bonding.In the absence of firm knowledge and effective mental models of chemical bonding, it almost impossible to achieve significant results in any chemical field or application. In this work, which combines the pure chemistry of bonding with didactical studies, I have used database searches, questionnaires, interviews, and textbook analyses to investigate some of the more important aspect of chemical bonding.In the field of pure Science, bond length data have been analysed to ascertain the differences in bond strength between neutral and charged ligands in coordination compounds. While the bond strengths differ, the difference is not sufficiently large for the bonds to be classified as different types.In the didactical field, the conceptual models of students in South Africa and Sweden and underlying causes for these mind-sets, have been investigated. The results show that the different curricula and points of emphasis foster different patterns of understanding of the topic. One finding is that 55%–60% of the students exposed to any of the curricula have a molecular view of a salt that can be traced to visual representations of single ions or formula units of a salt. Therefore, it is important to understand how, when, and which models to use, in order to help students build a more advanced understanding of chemical bonding.
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| 2. |
- Nimmermark, Anders, 1971, et al.
(författare)
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Metal-ligand bond lengths and strengths: are they correlated? A detailed CSD analysis
- 2013
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Ingår i: Zeitschfrift für Kristallographie. - : Walter de Gruyter GmbH. - 0044-2968. ; 228:7, s. 311-317
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Konferensbidrag (refereegranskat)abstract
- Structure data on metal-alkoxides, metal-alcohol, metal-carboxylates, metal-carboxylic acid, metal-azolate and metal-azole coordination compounds from the Cambridge Structural Database (CSD) were analysed in terms of bond lengths. In general the anionic ligands form shorter metal-ligand bonds by about 0.02-0.05 angstrom compared to neutral ligands, a clear indication of a charge contribution to the bonding interactions. This small difference is not, however, deemed as sufficient to generate two distinct classes of metal-ligand bonding. Instead, the anionic ligands can be viewed as having "charge assisted" metal-ligand bonding, corresponding to the same term used for "charge-assisted hydrogen bonding".
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| 3. |
- Nimmermark, Anders, 1971, et al.
(författare)
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Teaching of chemical bonding: a study of Swedish and South African students' conceptions of bonding
- 2016
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Ingår i: Chemistry Education Research and Practice. - : Royal Society of Chemistry (RSC). - 1109-4028 .- 1756-1108. ; 17:4, s. 985-1005
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Tidskriftsartikel (refereegranskat)abstract
- Almost 700 Swedish and South African students from the upper secondary school and first-term chemistry university level responded to our survey on concepts of chemical bonding. The national secondary school curricula and most common textbooks for both countries were also surveyed and compared for their content on chemical bonding. Notable differences between the countries were found in textbooks and in the curriculum regarding the topics of ionic bonding, bond energetics and use of the VSEPR model, the latter being absent in the Swedish curriculum and ionic bonding not explicitly mentioned in the South African curriculum. To some extent these differences are reflected in the students' responses to the survey. It is also clear that university teachers in both countries must prepare effective counter-measures against deep rooted misunderstandings. For the upper secondary school level it is suggested that the bond energetics and exothermic and endothermic reactions be clearly and carefully presented and separated as the study indicates that mixing of these two concepts is a major cause of confusion.
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