The Key to Naming Ionic Compounds and Acids
I strongly believe naming ionic compounds and acids can be greatly simplified by observing a few facts and memorizing the names and formulas of 12 polyatomic ions that have an ate suffix. The key in naming both ionic compounds and acids is the recognition of the anion [negative charged ion] present in the substance. If the anion consists of only one element its name is the root name of that element with an ide suffix.
Ionic compounds are named in the following way: the name of the metal element comes first followed by the name of the anion. Example – CaCl2 is named Calcium Chloride, Ca(ClO3)2 is named Calcium Chlorate. If you have memorized the key Oxy-anions with ate suffixes applying the following rules will expand your ability by threefold.
1) If the Oxy-anion has 1 less oxygen then the ate form it ends with ite instead: example SO42-is sulfate; SO32- is sulfite
2) If the Oxy-anion has 2 less oxygen then the ate form; it has a prefix of hypo and an ite suffix: example PO43- is phosphate; PO23- is hypophosphite
3) If the Oxy-anion has 1 more oxygen then the ate form; it has a prefix of per: example ClO31- is Chlorate; ClO41- is perchlorate
Recognition of the anion is also the key in naming the acid. If the anion present in the formula of the acid ends in ide, use the following procedure. The acid is named using a prefix of Hydro followed by the root name of the anion ending with an ic suffix. Example: HCl is named hydrochloric acid.
If the anion present in the acid ends in ate, you name it by taking the root name of the anion followed by an ic suffix. Example: HClO3 is named chloric acid.
If the anion in the acid ends in ite, you take the root name of the anion followed with an ous suffix. Example: HClO2 would be named chlorous acid.
Following the rule stated above for naming the anions, if the anion has one more oxygen than the ate form the acid would be named as follows: a prefix of per followed by the root name of the anion ending with an ic suffix. Example: HClO4 would be named perchloric acid. Finally if the anion has two less oxygens than the ate form [one less than the ite form] it would be named with a prefix of hypo followed by the rootname of the anion ending with an ous suffix. Example: HClO would be named hypochlorous acid.
Applying these ideas a student should be able to write the formula of any ionic compound or acid when given its name. The key is being able to correctly name the anion present and apply the rule accordingly. The key in my opinion is committing to memory the names and formulas of the main oxy-anions that end in ate. If you have questions or comments about this blog please email me.