As above, model a few examples, then give students an opportunity to practise, keeping your first examples varying only slightly, for example: sodium hydroxide, sodium sulfate, sodium carbonate, aluminium hydroxide, aluminium sulfate etc. You will also want to introduce polyatomic ions like sulfate, hydroxide and carbonate. You can also add written formulas as well like ‘sodium sulfide’ to help them realise how interconnected the topics are and that you can go from formulas to ions and from ions to formulas. Give them a lot more practice, mixing examples with different ionic ratios and stoichiometric numbers. Give students some more to practise, then pause and show them an example like 2Na 2O to marry this step with the previous step. Then show students a simple graphical way of writing the compound as ions: This enables you to test prerequisite knowledge, give your students the opportunity for retrieval practice and help your students see the connections between different topics. Use arrows to show what happens when they bond ionically.Draw the full atomic structure/electronic configuration of sodium and chlorine.Compounds into ionsįirst, give students some recall questions for the formation of a compound like sodium chloride along the lines of: To address these, we can sequence and segment as follows: 1. Appreciation of which substances can form ions and which ones cannot.Turning coefficients into subscript numbers.Turning subscript numbers into coefficients.Confusing charges with subscript numbers.In my experience, students have difficulty with: If we can isolate each difficulty, then we can teach them explicitly in turn and allow students’ skills to gradually build. We could start here with the most common problems students have when constructing these equations and use those to work backwards. Below is an example of how you might tackle this for one of the most challenging topics to teach at 14–16 chemistry: construction of ionic equations. If your segmenting is off, they won’t remember your explanation. If your sequencing is off, students won’t understand your explanation. In short, it determines the order in which topics are taught, and where you choose to break them up for students to have an opportunity to practise. Sequencing and segmenting is one of the most powerful concepts in a science teacher’s arsenal. Sequencing and segmenting a topic is key to students understanding and remembering information
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