Question

What is $F{{e}_{2}}{{(S{{O}_{4}})}_{3}}$ called?

Answer 1

Any compound is named with the respective atoms present in it. Ionic compounds consist of cations as positive species and anions as negative species. The naming is done in such a way that the name of the cation is written first and then the name of the anion is written. For transition metals, their respective valences in Roman numeral are also written after the cation.

Complete answer:
A chemical compound is given its name according to the atoms present in that molecule. Names are given to compounds regarding the rules by the international union for pure and applied chemistry (IUPAC). The nomenclature of ionic compounds consists of naming the cation first and then the anion.
We have been given $F{{e}_{2}}{{(S{{O}_{4}})}_{3}}$, where iron (Fe) is present and a sulfate ion. As we know iron is a transition metal from the d block, it has variable valences. Iron is the cation, while sulfate is the anion. Sulfate anion consists of a charge of -2 as it takes 2 electrons to complete its octet. So, from this, the valence of iron in $F{{e}_{2}}{{(S{{O}_{4}})}_{3}}$ can be calculated as,
$2Fe\times {{(S{{O}_{4}}^{2-})}_{3}}=0$ (as the net charge on a molecule is 0)
$2Fe\times (-2)3=0$
$2Fe=-6$
$Fe=\frac{6}{2}$
Fe = +3
Hence, the valence of Fe is +3, so it is in ferric form.
Now, we can write the name iron sulfate or ferric sulfate. As iron is the cation and sulfate is the anion.
Hence, the name of $F{{e}_{2}}{{(S{{O}_{4}})}_{3}}$ is iron (III) sulfate or ferric sulfate.

Note:
Iron with +2 oxidation state is called ferrous, while in +3 oxidation state is called ferric. We can identify the valence or the oxidation state of iron by the fact that sulfate anion is present in the quantity of 3. Therefore iron will be in the form of +3. To balance the -2 charges of sulfate iron is taken in a quantity of 2 in the oxidation state of $F{{e}^{3+}}$.