Sorry if this is the wrong place to be posting this question. I'm new to the forums. I haven't had chemistry since Sophomore year of high school. So it's been about 8 years. I'm trying to brush up before I take my placement exam for college.

 

My question is that I can't quite understand how you find different cation values for metals. i.e. In trying to name Fe(N O3)3 it is iron (III) nitrate.

 

How do I know when it is supposed to change it's charge value? Sorry if this is a simple question. I do not have a teacher, I am trying to self learn all of basic chemistry.

 

Please feel free to recommend any helpful chem sites or forum pages.

 

Thanks.

In reactions such as the reaction of iron with dilute acids, Fe 2+ salts are formed. but if an aqueous solution of an Fe 3+ salt undergoes a double decomposition reaction with an aqueous solution of another salt,(or with strong alkalis such as NaOH) the Fe 3+ salts are formed(with a different anion).