why calcium bromide is a satisfactory name from CaBr2, but FeBr2 must be called iron(II) bromide.
The correct answer and explanation is :
Calcium bromide (CaBr2) is a satisfactory name because calcium, as a Group 2 metal, always forms a +2 charge in its ionic compounds. Therefore, there is no ambiguity in the charge of calcium in this compound, and it is unnecessary to specify the oxidation state of calcium in the name. On the other hand, iron (Fe) is a transition metal, and it can have more than one oxidation state, which is why the oxidation state of iron must be specified in the name.
Explanation:
- Calcium (Ca): Calcium is in Group 2 of the periodic table and, like all alkaline earth metals, it consistently forms ions with a +2 charge. When calcium reacts with bromine (Br), each calcium ion (Ca²⁺) combines with two bromide ions (Br⁻) to form the ionic compound CaBr2. Since calcium always has a +2 charge in its compounds, there is no need to specify the oxidation state of calcium in the name. Therefore, the name “calcium bromide” is sufficient to describe the compound.
- Iron (Fe): Iron is a transition metal, and transition metals can form multiple positive oxidation states. Iron can exist in the +2 oxidation state (Fe²⁺) and the +3 oxidation state (Fe³⁺), among others. When iron forms a compound with bromine, such as FeBr2, it can be in the +2 oxidation state (Fe²⁺) or the +3 oxidation state (Fe³⁺), depending on the specific compound. To avoid ambiguity, the oxidation state of iron must be indicated in the name. In the case of FeBr2, iron is in the +2 oxidation state, so the name must specify this by calling it “iron(II) bromide.”
In summary, the name “calcium bromide” is sufficient because calcium has a fixed charge of +2, while the name “iron(II) bromide” specifies the oxidation state of iron, which can vary. This distinction ensures clarity and accuracy in naming ionic compounds.