Dr. Keith S. Taber
Publication:
Taber, K. S. (2002)
Compounding quanta - probing the frontiers of student understanding of molecular
orbitals
Chemistry Education: Research and Practice in Europe, 3 (2), pp.159-173.
Abstract:
College level students are expected to be able to make sense of, and explain,
aspects of chemical bonding and structure in terms of molecular orbital concepts.
The present paper derives from in-depth research into the thinking of a small
sample of college chemistry students. This study in one UK college revealed
the ways in which students found the orbital concept problematic. A previous
paper ("Conceptualizing quanta: illuminating
the ground state of student understanding of atomic orbitals") reports
how these students struggled to make sense of atomic structure in orbital
terms. The present paper considers the students' understanding of the molecular
orbital concept. It is suggested that when learners are introduced to ideas
about molecular orbitals before they have mastered ideas about atomic systems,
then their learning difficulties may be 'compounded' in the more complex
context. For example, it was found that students often identified the orbitals
involved in two-centre bonds as atomic orbitals. Representations of delocalised
bonds invoked various alternative interpretations: but were seldom conceptualised
as implying poly-centred molecular orbitals. These findings suggest that
students are not given sufficient time to construct acceptable models of
atoms and molecules as 'quanticles'.
KEY WORDS: students' conceptions; quanta; orbitals; bond formation;
molecular structure; molecular orbitals