Nomenclature with iron chloride

If the cation and anion exist in only one common charged form, there is no ambiguity between formula and name. Sodium chloride must be NaCl, and lithium sulfide must be Li2S, so that the sum of positive and negative charges is zero. With many elements, such as the transition metals, several ions of different charge may exist. Fe ", Fe + and Cu+, Cu + are two common examples. Clearly, an ambiguity exists if we use the name iron for both Fe + and Fe + or copper for both Cu" and Cu +. Two systems have been developed to avoid this problem the Stock system and the common nomenclature system. 

The nomenclature of the compounds of the metals is also based upon their oxidation states. At the present time there are two principal nomenclatures in use. We may illustrate the two systems of nomenclature by taking the compounds FeCl2 and FeCla as examples. In the older system a compound of a metal in the lower of two important oxidation states is named by use of the name of the metal (usually the Latin name) with the suffix OHS. Thus the salts of iron in oxidation state -f2 are ferrous salts FeCl2 is called ferrous chloride. The compounds of a metal in the higher oxidation state are named with use of the suffix ic. The salts of iron in oxidation state -1-3 are called ferric salts FeCIs is ferric chloride. 

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