Question

Why do we call \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}\) barium nitrate, but we call \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) iron(II) nitrate?

Short answer

We call \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}\) barium nitrate because barium, an alkaline earth metal, has only one possible charge (\(\mathrm{Ba}^{2+}\)). However, we call \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) iron(II) nitrate because iron, a transition metal, can have different charges. In this case, it has a \(\mathrm{Fe}^{2+}\) charge, so we specify the oxidation state using a Roman numeral in parentheses – iron(II).

Step-by-step solution

Analyze the chemical formula for barium nitrate

Since barium is a member of the alkaline earth metals group, it only has one possible charge, \(\mathrm{Ba}^{2+}\). So in the compound \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}\), there will be no confusion regarding the charge of barium.

Naming barium nitrate

As there is no ambiguity in the oxidation state of barium, we can simply name the compound by combining the names of cation and anion: barium nitrate.

Analyze the chemical formula for iron(II) nitrate

In the compound \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\), the cation is iron, which is a transition metal that can have different charges. In this case, it has a charge of \(\mathrm{Fe}^{2+}\). To indicate the specific oxidation state of iron, we will use a Roman numeral in parentheses after the cation's name.

Naming iron(II) nitrate

Given that the iron cation has a \(2+\) charge, we write the name as iron(II), followed by the name of the anion, nitrate. So the compound is named iron(II) nitrate.