Mr. Groves Explains...

Why Memorize Ions?

Although it seems that there are an infinite number and variety of compounds in chemistry, ultimately, there are two major types of compounds... ionic compounds and covalent compounds.

Many of the details of these two compounds are the same, but there are differences as well. For instance, ionic compounds are named by listing the positive and the negative ion, whereas covalent compounds require you to state the number and kind of each atom.

Naming Ionic vs. Covalent Compounds
Al2S3 N2O3
aluminum sulfide dinitrogen trioxide

So... a valuable skill will be to RECOGNIZE when a compound is made up of ions. It is not a simple matter to look at a chemical formula and state whether the compound is ionic or covalent. Some elements are ionic in one case and covalent in another case. Some compounds even depend on whether they are dissolved in water or not (e.g. acids.)

The bottom line is simply that if you see a compound in which you recognize a positive and a negative ion, it is an ionic compound. Otherwise, it is a covalent compound. To make this recognition, you must have the list of ions in your head.