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 has a fixed oxidation state of +2 and there is no ambiguity in the charge. In contrast, we call \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) iron(II) nitrate because iron can form multiple oxidation states, and the (II) in the name specifies that it has a +2 charge in this particular compound.

Step-by-step solution

Understanding Ionic Compounds

Barium nitrate and iron(II) nitrate are ionic compounds, which are formed between metal and non-metal ions, specifically a positive ion (cation) and a negative ion (anion). In these compounds, the metal (cation) is written first and the non-metal (anion) is written second.

Barium Nitrate

Barium nitrate has the chemical formula \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}\). In this compound, Ba is the symbol for barium and it is an alkaline earth metal. The (NO3) group represents the nitrate ion with a -1 charge. Since barium has an oxidation state of +2 and always forms 2+ cations, there is no ambiguity in the charge, and we simply call it barium nitrate.

Iron(II) Nitrate

Iron(II) nitrate has the chemical formula \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\). In this compound, Fe is the symbol for iron, which is a transition metal and can form different oxidation states. The nitrate ion (NO3) has a -1 charge. Since iron can have multiple positive charges as cations (+2 and +3 are common), we need to specify which iron cation is present in the compound. In this case, Fe has a +2 charge in the compound as there are two nitrate ions present, so we call it iron(II) nitrate to indicate the oxidation state or charge of the iron.

Summary

To recap, we call \(\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}\) barium nitrate because barium has a fixed oxidation state of +2 and there is no ambiguity in the charge. In contrast, we call \(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{2}\) iron(II) nitrate because iron can form multiple oxidation states, and the (II) in the name specifies that it has a +2 charge in this particular compound.