Question

The molecular formula of Iron (III) sulfide is:
A. \[Fe{S_3}\]
B. \[F{e_2}{S_3}\]
C. \[Fe{S_2}\]
D. \[F{e_3}{S_4}\]

Answer 1

Hint: Iron is a d- block metal. The d block elements are found in the group 3,4,5,6,7,8,9,10,10,11 and 12 of the periodic table. These are also known as transition metals. The d orbital is filled with an electronic shell $n - 1$ . There are a total of 40 d block elements.

Complete step by step answer:
The d block elements are small in size and generally have high electron positive density.
They consist of $(n - 1)$ d free orbitals to accept the free electrons from the ligand and hence, form complexes easily.
In the case of Iron (III) sulfide, the oxidation state of iron is +3. And the charge of sulfide ion is -3. Therefore, to have total charge zero, the number of iron ions and sulfide ions are 2 and 3 respectively.
Therefore, the molecular formula of this compound is, \[F{e_2}{S_3}\]
So, the correct answer is B.

Additional information:
The given compound is a coordination compound. To find the IUPAC name for the given compound, we need to follow some rules:
1.Name the ions present in the compound in the order such that the name of the cation Is placed before the anion.
2.When naming within the complexion, before we write the name of the central atom, we write the name of the ligands present.
3.The names of the ligands must be written in alphabetic order.
4.In case a certain ligand is repeated, then it needs to have certain prefixes to denote the number of times it has been repeated. The prefixes mono-, di-, tri-, are used for once, twice, and thrice repetitions respectively.
5.If the ligand name is enclosed in parentheses and its number is given with the alternate prefixes bis, tris, terraces instead.
6.To denote the oxidation number of the central atom, the corresponding roman numeral must be included in parenthesis and be written after writing the name of the central atom.
7.When the central atom is negative, then we add the suffix ‘-ate’ to the name of the central atom

Note:Transition elements show a magnetic moment due to the presence of unpaired electrons to their d orbitals. With increasing the number of unpaired electrons, the spin magnetic moment value increases and vice-versa. If there is no unpaired electron then it is diamagnetic.