Mark’s examples were now more focused towards the intended object of learning and
instead of only giving the students a large number of examples he uses examples and
tasks which put the emphasis on the differences instead of on the concepts alone. He
used a task with pictures of models of atoms and ions and the students should decide
if the model illustrated an atom or an ion. In his second lesson, Mark managed to
provide examples that were more focused with fewer concepts involved. His strategy
in lesson 1 (i.e. to use a variation of explanations) was now changed into a strategy
where variation was used as a way to focus. On the whiteboard, he drew an atom and
an ion and highlighted the differences and similarities in order to make the students
understand them both. Further, when he chose examples in his second lesson he
built on his previous experiences of students’ previous knowledge and misconceptions
that also made him use examples to clarify how electrons move around the nucleus
and further, how electrons can move from one energy level to another.