Desarrollo de una unidad didáctica : el estudio del enlace químico en el bachillerato

The planning and development of didactic units is an unbeatable element for preparing a set of lessons based on a constructivist approach, within the framework of a pedagogical content knowledge that impacts on science learning. We are presenting the details of the scientific and didactical analysis, also of the selection of objectives, pedagogical and assessment strategies for the presentation of the «chemical bonding» topic to two groups of students. We have reached several positive conclusions that include improvement on the fi nal objective of the didactic unit, trying to reach a general description of chemical bonding in which the selection of models on it (covalent, ionic, metallic, residual, etc.) responds to different approaches of essentially the same electrostatic phenomenon.