Problem 14 - Chemistry An Atoms First Approach

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?

Step-by-Step Solution

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 1: 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.

Step 2: 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.

Step 3: 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.

Step 4: 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.