This resource, from the Royal Society of Chemistry, covers the driving force of chemical reactions and why reactions occur. Students are provided with diagrams showing electron arrangements in a hydrogen atom, hydrogen molecule, fluorine atom, fluorine molecule and hydrogen fluoride. They are asked to explain, using these diagrams, why the reaction occurs between hydrogen and fluorine.
This activity may be used before teaching about energetics to elicit prior conceptions, or after teaching to see if the intended learning has taken place. The activity may also be used to elicit the ideas of students aged 14-16, although students at this level may not have been taught a scientifically valid explanation for why reactions occur.