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I recently came across a practice problem in my textbook asking me to name a few compounds using -ic and -ous endings. The exact wording is:

Write the name of each of the following ionic substances, using -ous and -ic endings to indicate the charge of the cation.

The first one was CoCl2. However, cobalt has more than just two oxidization states (3, 2, 0, and -1).

So if it is one of the states in the middle, how do I decide whether to use -ous or -ic

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up vote 7 down vote accepted

Cobalt may possibly have all those other oxidation states (and others too) for this nomenclature system, we only care about the two most common oxidation states in ionic compounds: $\ce{Co^{2+}}$ and $\ce{Co^{3+}}$. Cobalt(II) compounds would thus be named cobaltous and cobalt(III) compounds would be cobaltic. Which is yours?

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Chloride is -1 and it's Cl2 so Cobaltous. Thanks! – 735Tesla Jul 31 '14 at 0:38
-1 as in the charge, not your answer. That was really helpful! +1 – 735Tesla Jul 31 '14 at 0:38
Is there a reference you would recommend for finding the most common oxidization states? I can't find one in my book and online. – 735Tesla Jul 31 '14 at 1:59

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