Answer
We call Ba(NO$_{3}$)$_{2}$ barium nitrate because there is no ambiguity here. Barium usually has an oxidation number of 2+ because it belongs the alkaline earth metals and readily loses its two valence electrons to an electron acceptor.
With Fe(NO$_{3}$)$_{2}$, we have to specify which iron we are talking about. Iron (Fe) is a transition metal, and, usually, transition metals have several oxidation numbers. Iron has common oxidation numbers of 2+ and 3+.
Work Step by Step
We call Ba(NO$_{3}$)$_{2}$ barium nitrate because there is no ambiguity here. Barium usually has an oxidation number of 2+ because it belongs the alkaline earth metals and readily loses its two valence electrons to an electron acceptor.
With Fe(NO$_{3}$)$_{2}$, we have to specify which iron we are talking about. Iron (Fe) is a transition metal, and, usually, transition metals have several oxidation numbers. Iron has common oxidation numbers of 2+ and 3+.
