There are two types of binary compounds (compounds that contain only two elements) you will encounter. They will either be ionic or molecular (covalent). The nomenclature system is different for the two types of compounds. N2O4 dinitrogen tetraoxide Fe2O3 iron(II) oxide NCl3 nitrogen trichloride CoCl2 cobalt(II) chloride 3. Classify each compound in the model as either ionic or molecular. 4. Which class of compounds uses Greek prefixes? 5. Which class of compounds uses Roman numerals? 6. Write a sentence or two that will help you remember the nomenclature rules for the two classes of compounds