Review electronegativity definition. Use a compound known to exhibit ionic characteristics, and a compound known to exhibit covalent characteristics. From these two compounds, determine the difference in the electronegativity numbers of each element in each compound. Elicit that the ionic compound shows a high difference compared to the covalent compound. Determine a general rule which covers how to determine the type of bond. For the second class, perform a lab demonstration which will indicate that a chemical reaction has occured.